PHP String strstr() Function

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The PHP String strstr() function is used to find for the first occurrence of a string within another string and shows the section of the latter beginning with the first occurrence of the initial string (if given). This function is case sensitive.

It is a binary-safe function, which means it can be used on binary files without changing their content. The strstr() function is similar to the stristr() function, with the only difference is that stristr() is case-insensitive while strstr() is case-sensitive.

Syntax

Below is the syntax of the PHP String strstr() function −

string strstr ( 
   string $string, 
   string $search, 
   bool $before_search = false 
)

Parameters

Here are the parameters of the strstr() function −

• $string − (Required) It indicates the string that will be searched. In other words, it is the primary string argument in which the $search value is searched.

• $search − (Required) It specifies the string that will be searched in the $string parameter. If this option provides a number or integer value rather than a string, it will look for a character that matches the ASCII value for that number.

• $before_search − (Optional) It defines the Boolean value, which has the default value of FALSE. If we set it to TRUE, it will return the portion of the string that precedes the first occurrence of the search parameter.

Return Value

The strstr() function returns the remaining string (from the matching point), or FALSE if the string being searched for is not found.

PHP Version

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

Example 1

Here is the basic example of the PHP String strstr() function to find the first occurrence of a string in the given string.

<?php
   // define string here
   $string = "Hello, welcome to PHP programming!";
   $search = "welcome";

   // Using strstr to find the first occurrence of "welcome"
   $result = strstr($string, $search);

   echo $result; 
?>

Output

Here is the outcome of the following code −

welcome to PHP programming!

Example 2

In the below PHP code we will try to use the strstr() function and see the case sensitivity of this function.

<?php
   // Demonstrating case sensitivity
   $string = "Hello, Welcome to PHP programming!";
   $search = "welcome";

   // Using strstr with a case mismatch
   $result = strstr($string, $search);

   if ($result === false) {
      echo "Substring not found because of case mismatch.";
   } else {
      echo $result;
   }
?> 

Output

This will generate the below output −

Substring not found because of case mismatch.

Example 3

Now the below code uses strstr() function with the optional $before_search parameter which is set to true.

<?php
   // Define string here
   $string = "PHP is powerful and versatile.";
   $search = "powerful";

   // Using strstr to get the part before "powerful"
   $result = strstr($string, $search, true);

   echo $result; 
?> 

Output

This will create the below output −

PHP is 

Example 4

In the following example, we are using the strstr() function to show how to search using an ASCII value.

<?php
   // Define string here
   $string = "Find the first comma, if there is one.";
   
   // ASCII value for ','
   $asciiValue = 44; 

   $result = strstr($string, chr($asciiValue));

   if ($result) {
      echo "Substring starting from comma: $result";
   } else {
      echo "Comma not found in the string.";
   }
?> 

Output

Following is the output of the above code −

Substring starting from comma: , if there is one