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