PHP Variable Handling is_string() Function

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The PHP Variable Handling is_string() function is used to check whether a given variable is a string. A string is a type of data that includes characters, integers, and symbols within provide marks. This function is useful for determining whether a value is a string before using it. It helps to avoid program errors.

If the variable is a string, the function returns true. If the variable isn't a string, it returns false. It supports PHP 4, 5, 7, and 8. This function is basic and easy to use.

Syntax

Below is the syntax of the PHP Variable Handling is_string() function −

 bool is_string ( mixed $value ) 

Parameters

This function accepts $value parameter which is the variable that we want to check.

Return Value

The is_string() function returns TRUE if the variable is a string. And the function returns FALSE if the variable is not a string.

PHP Version

First introduced in core PHP 4, the is_string() function continues to function easily in PHP 5, PHP 7, and PHP 8.

Example 1

Here is the basic example of the PHP Variable Handling is_string() function to check if a given variable is a string. If the variable contains a string, it returns true, otherwise false.

 <?php // Assigning a string to variable $var = "Hello, PHP!"; if (is_string($var)) { echo "Yes, this is a string."; } else { echo "No, this is not a string."; } ?> 

Output

Here is the outcome of the following code −

 Yes, this is a string. 

Example 2

In the below PHP code we will use the is_string() function and check a number vs string. So the program tests both a string and a number. It confirms that only the string returns true.

 <?php // String containing numbers $var1 = "123"; // Integer $var2 = 123; echo is_string($var1) ? "var1 is a string.\n" : "var1 is not a string.\n"; echo is_string($var2) ? "var2 is a string.\n" : "var2 is not a string.\n"; ?> 

Output

This will generate the below output −

 var1 is a string. var2 is not a string. 

Example 3

The PHP program below shows the is_string() method by checking various different types of variables. The is_string() method checks if a variable is a string or not. It returns "string" when the variable is a string and "not string" otherwise.

 <?php $a = "Tutorialspoint"; echo "a is ".( is_string($a)? 'string' : 'not string') . "\n"; $b = 0; echo "b is ".( is_string($b)? 'string' : 'not string') . "\n"; $c = 40; echo "c is ".( is_string($c)? 'string' : 'not string') . "\n"; $d = NULL; echo "d is ".( is_string($d)? 'string' : 'not string') . "\n"; $e = array("a", "b", "c"); echo "e is ".( is_string($e)? 'string' : 'not string') . "\n"; $f = 3.1416; echo "f is ".( is_string($f)? 'string' : 'not string') . "\n"; $g = new stdClass(); echo "g is ".( is_string($g)? 'string' : 'not string') . "\n"; $h = ''; echo "h is ".( is_string($h)? 'string' : 'not string') . "\n"; ?> 

Output

This will create the below output −

 a is string b is not string c is not string d is not string e is not string f is not string g is not string h is string