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>String Variables in PHP

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String variables are used for values that contains characters.

In this chapter we are going to look at the most common functions and operators used to manipulate strings in PHP.

After we create a string we can manipulate it. A string can be used directly in a function or it can be stored in a variable.

Below, the PHP script assigns the text "Hello World" to a string variable called $txt:

<?php
$txt="Hello World";
echo $txt;
?>

The output of the code above will be:

Hello World

Now, lets try to use some different functions and operators to manipulate the string.



The Concatenation Operator


There is only one string operator in PHP.

The concatenation operator (.)  is used to put two string values together.

To concatenate two string variables together, use the concatenation operator:



<?php
$txt1="Hello World!";
$txt2="What a nice day!";
echo $txt1 . " " . $txt2;
?>

The output of the code above will be:

Hello World! What a nice day!

If we look at the code above you see that we used the concatenation operator two times. This is because we had to insert a third string (a space character), to separate the two strings.



The strlen() function


The strlen() function is used to return the length of a string.

Let's find the length of a string:



<?php
echo strlen("Hello world!");
?>

The output of the code above will be:

12

The length of a string is often used in loops or other functions, when it is important to know when the string ends. (i.e. in a loop, we would want to stop the loop after the last character in the string).



The strpos() function


The strpos() function is used to search for character within a string.

If a match is found, this function will return the position of the first match. If no match is found, it will return FALSE.

Let's see if we can find the string "world" in our string:



<?php
echo strpos("Hello world!","world");
?>

The output of the code above will be:

6

The position of the string "world" in our string is position 6. The reason that it is 6 (and not 7), is that the first position in the string is 0, and not 1.

Some more String Functions For Beginner's..








chr()


 


Definition and Usage


The chr() function returns a character from the specified ASCII value.

Syntax


chr(ascii)

Parameter
Description

ascii
Required. An ASCII value



Tips and Notes


Note: The x parameter can be specified in decimal, octal, or hex values. Octal values are defined by a leading 0, while hex values are defined by a leading 0x.



Example



<?php
echo chr(52)."<br />";
echo chr(052)."<br />";
echo chr(0x52)."<br />";
?>

The output of the code above will be:

4
*
R

 








echo()


 


Definition and Usage


The echo() function outputs one or more strings.

Syntax


echo(strings)

Parameter
Description

strings
Required. One or more strings to be sent to the output



Tips and Notes


Note: The echo() function is not actually a function, so you are not required to use parentheses with it. However, if you want to pass more than one parameter to echo(), using parentheses will generate a parse error.

Tip: The echo() function is slightly faster than print().

Tip: The echo() function has the following shortcut syntax. See example 5.



Example 1



<?php
$str = "Who's Kai Jim?";
echo $str;
echo "<br />";
echo $str."<br />I don't know!";
?>

The output of the code above will be:

Who's Kai Jim?
Who's Kai Jim?
I don't know!



Example 2



<?php
echo "This text
spans multiple
lines.";
?>

The output of the code above will be:

This text spans multiple lines.



Example 3



<?php
echo 'This ','string ','was ','made ','with multiple parameters';
?>

The output of the code above will be:

This string was made with multiple parameters



Example 4


Difference of single and double quotes. Single quotes will print the variable name, not the value:



<?php
$color = "red";
echo "Roses are $color";
echo "<br />";
echo 'Roses are $color';
?>

The output of the code above will be:

Roses are red
Roses are $color



Example 5


Shortcut syntax:



<html>
<body>
<?php
$color = "red";
?>
<p>Roses are <?=$color?></p>
</body>
</html>

 







fprintf()

 


Definition and Usage


The fprintf() function writes a formatted string to a specified output stream (example: file or database).

The arg1, arg2, ++ parameters will be inserted at percent (%) signs in the main string. This function works "step-by-step". At the first % sign, arg1 is inserted, at the second % sign, arg2 is inserted, etc.

The fprintf() function returns the length of the written string.

Syntax


fprintf(stream,format,arg1,arg2,arg++)

Parameter
Description

stream
Required. Specifies where to write/output the string

format
Required. Specifies the string and how to format the variables in it.

Possible format values:


  • %% - Returns a percent sign
  • %b - Binary number
  • %c - The character according to the ASCII value
  • %d - Signed decimal number
  • %e - Scientific notation (e.g. 1.2e+2)
  • %u - Unsigned decimal number
  • %f - Floating-point number (local settings aware)
  • %F - Floating-point number (not local settings aware)
  • %o - Octal number
  • %s - String
  • %x - Hexadecimal number (lowercase letters)
  • %X - Hexadecimal number (uppercase letters)

Additional format values. These are placed between the % and the letter (example %.2f):


  • + (Forces both + and - in front of numbers. By default, only negative numbers are marked)
  • ' (Specifies what to use as padding. Default is space. Must be used together with the width specifier. Example: %'x20s (this uses "x" as padding)
  • - (Left-justifies the variable value)
  • [0-9] (Specifies the minimum width held of to the variable value)
  • .[0-9] (Specifies the number of decimal digits or maximum string length)

Note: If multiple additional format values are used, they must be in the same order as above.

arg1
Required. The argument to be inserted at the first %-sign in the format string

arg2
Optional. The argument to be inserted at the second %-sign in the format string

arg++
Optional. The argument to be inserted at the third, fourth, etc. %-sign in the format string



Tips and Notes


Note: If there are more % signs than arguments, you must use placeholders. A placeholder is inserted after the % sign, and consists of the argument- number and "\$". See example three.

Tip: Related functions: printf(), sprintf(), vfprintf(), vprintf(), and vsprintf().



Example 1



<?php
$str = "Hello";
$number = 123;
$file = fopen("test.txt","w");
echo fprintf($file,"%s world. Day number %u",$str,$number);
?>

The output of the code above will be:

27

The following text will be written to the file "test.txt":

Hello world. Day number 123



Example 2



<?php
$number = 123;
$file = fopen("test.txt","w");
fprintf($file,"%f",$number);
?>

The following text will be written to the file "test.txt":

123.000000



Example 3


Use of placeholders:



<?php
$number = 123;
$file = fopen("test.txt","w");
fprintf($file,"With 2 decimals: %1\$.2f
\nWith no decimals: %1\$u",$number);
?>

The following text will be written to the file "test.txt":

With 2 decimals: 123.00
With no decimals: 123


 








ltrim()


 


Definition and Usage


The ltrim() function will remove whitespaces or other predefined character from the left side of a string.

Syntax


ltrim(string,charlist)

Parameter
Description

string
Required. Specifies the string to check

charlist
Optional. Specifies which characters to remove from the string. If omitted, all of the following characters are removed:


  • "" - NULL
  • "\t" - tab
  • "\n" - new line
  • "\x0B" - vertical tab
  • "\r" - carriage return
  • " " - ordinary white space



Example 1



<html>
<body>
<?php
$str = "    Hello World!";
echo "Without ltrim: " . $str;
echo "<br />";
echo "With ltrim: " . ltrim($str);
?>
<body>
<html>

The browser output of the code above will be:

Without ltrim: Hello World!
With ltrim: Hello World!

If you select "View source" in the browser window, you will see the following HTML:



<html>
<body>
Without ltrim:    Hello World!<br />With ltrim: Hello World!
</body>
</html>



Example 2



<?php
$str = "\r\nHello World!";
echo "Without ltrim: " . $str;
echo "<br />";
echo "With ltrim: " . ltrim($str);
?>

The browser output of the code above will be:

Without ltrim: Hello World!
With ltrim: Hello World!

If you select "View source" in the browser window, you will see the following HTML:

 



<html>
<body>
Without ltrim: 
Hello World!<br />With ltrim: Hello World!
</body>
</html>




 


 









printf()


 


Definition and Usage


The printf() function outputs a formatted string.

The arg1, arg2, ++ parameters will be inserted at percent (%) signs in the main string. This function works "step-by-step". At the first % sign, arg1 is inserted, at the second % sign, arg2 is inserted, etc.

Syntax


printf(format,arg1,arg2,arg++)

Parameter
Description

format
Required. Specifies the string and how to format the variables in it.

Possible format values:


  • %% - Returns a percent sign
  • %b - Binary number
  • %c - The character according to the ASCII value
  • %d - Signed decimal number
  • %e - Scientific notation (e.g. 1.2e+2)
  • %u - Unsigned decimal number
  • %f - Floating-point number (local settings aware)
  • %F - Floating-point number (not local settings aware)
  • %o - Octal number
  • %s - String
  • %x - Hexadecimal number (lowercase letters)
  • %X - Hexadecimal number (uppercase letters)

Additional format values. These are placed between the % and the letter (example %.2f):


  • + (Forces both + and - in front of numbers. By default, only negative numbers are marked)
  • ' (Specifies what to use as padding. Default is space. Must be used together with the width specifier. Example: %'x20s (this uses "x" as padding)
  • - (Left-justifies the variable value)
  • [0-9] (Specifies the minimum width held of to the variable value)
  • .[0-9] (Specifies the number of decimal digits or maximum string length)

Note: If multiple additional format values are used, they must be in the same order as above.

arg1
Required. The argument to be inserted at the first %-sign in the format string

arg2
Optional. The argument to be inserted at the second %-sign in the format string

arg++
Optional. The argument to be inserted at the third, fourth, etc. %-sign in the format string



Tips and Notes


Note: If there are more % signs than arguments, you must use placeholders. A placeholder is inserted after the % sign, and consists of the argument- number and "\$". See example three.

Tip: Related functions: fprintf(), sprintf(), vfprintf(), vprintf(), and vsprintf().



Example 1



<?php
$str = "Hello";
$number = 123;
printf("%s world. Day number %u",$str,$number);
?>

The output of the code above will be:

Hello world. Day number 123



Example 2



<?php
$number = 123;
printf("%f",$number);
?>

The output of the code above will be:

123.000000



Example 3


Use of placeholders:



<?php
$number = 123;
printf("With 2 decimals: %1\$.2f
<br />With no decimals: %1\$u",$number);
?>

The output of the code above will be:

With 2 decimals: 123.00
With no decimals: 123


 









 


rtrim()


 


Definition and Usage


The rtrim() function will remove whitespaces or other predefined character from the right side of a string.

Syntax


rtrim(string,charlist)

Parameter
Description

string
Required. Specifies the string to check

charlist
Optional. Specifies which characters to remove from the string. If omitted, all of the following characters are removed:


  • "" - NULL
  • "\t" - tab
  • "\n" - new line
  • "\x0B" - vertical tab
  • "\r" - carriage return
  • " " - ordinary white space



Example 1



<html>
<body>
<?php
$str = "Hello World!    ";
echo "Without rtrim: " . $str;
echo "<br />";
echo "With rtrim: " . rtrim($str);
?>
<body>
<html>

The browser output of the code above will be:

Without rtrim: Hello World!
With rtrim: Hello World!

If you select "View source" in the browser window, you will see the following HTML:



<html>
<body>
Without rtrim: Hello World!    <br />With rtrim: Hello World!
</body>
</html>



Example 2



<?php
$str = "Hello World!\r\n";
echo "Without rtrim: " . $str;
echo "<br />";
echo "With rtrim: " . rtrim($str);
?>

The browser output of the code above will be:

Without rtrim: Hello World!
With rtrim: Hello World!

If you select "View source" in the browser window, you will see the following HTML:



<html>
<body>
Without rtrim: Hello World!
<br />With rtrim: Hello World!
</body>
</html>



 


 









 


str_split()


 


Definition and Usage


The str_split() function splits a string into an array.

Syntax


str_split(string,length)

Parameter
Description

string
Required. Specifies the string to split

length
Optional. Specifies the length of each array element. Default is 1



Tips and Notes


Note: If length is less than 1, the str_split() function will return FALSE.

Note: If length is larger than the length of string, the entire string will be returned as the only element of the array.



Example 1



<?php
print_r(str_split("Hello"));
?>

The output of the code above will be:

Array
(
[0] => H
[1] => e
[2] => l
[3] => l
[4] => o
)



Example 2



<?php
print_r(str_split("Hello",3));
?>

The output of the code above will be:

Array
(
[0] => Hel
[1] => lo
)

 









 


str_word_count()


 


Definition and Usage


The str_word_count() function counts the number of words in a string.

Syntax


str_word_count(string,return,char)

Parameter
Description

string
Required. Specifies the string to check

return
Optional. Specifies the return value of the str_word_count() function.

Possible values:


  • 0 - Default. Returns the number of words found
  • 1 - Returns an array with the words from the string
  • 2 - Returns an array where the key is the position of the word in the string, and value is the actual word

char
Optional. Specifies special characters to be considered as words.

Note: This parameter was added in PHP 5.1



Example 1



<?php
echo str_word_count("Hello world!");
?>

The output of the code above will be:

2



Example 2



<?php
print_r(str_word_count("Hello world!",1));
?>

The output of the code above will be:

Array
(
[0] => Hello
[1] => world
)



Example 3



<?php
print_r(str_word_count("Hello world!",2));
?>

The output of the code above will be:

Array
(
[0] => Hello
[6] => world
)



Example 4


str_word_count() without and with the char parameter:



<?php
print_r(str_word_count("Hello world & good morning!",1));
print_r(str_word_count("Hello world & good morning!",1,"&"));
?>

The output of the code above will be:

Array
(
[0] => Hello
[1] => world
[2] => good
[3] => morning
)
Array
(
[0] => Hello
[1] => world
[2] => &
[3] => good
[4] => morning
)



 









 


str_replace()


 


Definition and Usage


The str_replace() function replaces some characters with some other characters in a string.

This function works by the following rules:


  • If the string to be searched is an array, it returns an array
  • If the string to be searched is an array, find and replace is performed with every array element
  • If both find and replace are arrays, and replace has fewer elements than find, an empty string will be used as replace
  • If find is an array and replace is a string, the replace string will be used for every find value

Syntax


str_replace(find,replace,string,count)

Parameter
Description

find
Required. Specifies the value to find

replace
Required. Specifies the value to replace the value in find

string
Required. Specifies the string to be searched

count
Optional. A variable that counts the number of replacements



Tips and Notes


Note: This function is case-sensitive. Use str_ireplace() to perform a case-insensitive search.

Note: This function is binary-safe.



Example 1



<?php
echo str_replace("world","Peter","Hello world!");
?>

The output of the code above will be:

Hello Peter!



Example 2


In this example we will demonstrate str_replace() with an array and a count variable:



<?php
$arr = array("blue","red","green","yellow");
print_r(str_replace("red","pink",$arr,$i));
echo "Replacements: $i";
?>

The output of the code above will be:

Array
(
[0] => blue
[1] => pink
[2] => green
[3] => yellow
)
Replacements: 1



Example 3


In this example we will demonstrate str_replace() with less elements in replace than find:



<?php
$find = array("Hello","world");
$replace = array("B");
$arr = array("Hello","world","!");
print_r(str_replace($find,$replace,$arr));
?>

The output of the code above will be:

Array
(
[0] => B
[1] =>
[2] => !
)


 


 


To be continued ………..

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