PHP String soundex() Function

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The PHP String soundex() function is used to calculate the Soundex key for a given string. The soundex key is a four-character alphanumeric string (beginning with a letter) that reflects the English pronunciation of a given string.

Soundex keys have the the nature of producing the same soundex key for words pronounced the same, making them useful for simplifying searches in databases when you know the pronunciation but not the spelling.

Syntax

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

string soundex ( string $string )

Parameters

This function accepts $string parameter which is a string to check. And it is the required parameter for this function.

Return Value

The soundex() function returns the soundex key as a four-character string. If at least one letter is found in the string, the resulting string begins with that letter. Otherwise, "0000" is returned.

PHP Version

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

Example 1

Here we will show you the basic example of the PHP String soundex() function to calculate the soundex key for the given string.

<?php
   // Input string
   $word = "Example";

   // Calculate the Soundex key
   $soundexKey = soundex($word);

   // Display the result
   echo "The Soundex key for '$word' is: $soundexKey";
?>

Output

Here is the outcome of the following code −

The Soundex key for 'Example' is: E251

Example 2

In the below PHP code, we will use the soundex() function and calculate the Soundex keys for an array of words.

<?php
   // Array of strings
   $strings = ["Example", "Examine", "Output", "Echo"];

   // Loop over each word and calculate its Soundex key
   foreach ($strings as $word) {
      echo "The Soundex key for '$word' is: " . soundex($word) . "\n";
   }
?> 

Output

This will generate the below output −

The Soundex key for 'Example' is: E251
The Soundex key for 'Examine' is: E255
The Soundex key for 'Output' is: O313
The Soundex key for 'Echo' is: E200

Example 3

This PHP program checks if two words sound similar by comparing their Soundex keys using the soundex() function.

<?php
   // Two words to compare
   $string1 = "Rupal";
   $string2 = "Rupali";

   // Calculate Soundex keys
   $soundex1 = soundex($string1);
   $soundex2 = soundex($string2);

   // Check if they sound similar
   if ($soundex1 === $soundex2) {
      echo "'$string1' and '$string2' sound similar.\n";
   } else {
      echo "'$string1' and '$string2' do not sound similar.\n";
   }
?> 

Output

This will create the below output −

'Rupal' and 'Rupali' sound similar.

Example 4

In the following example, we are using the soundex() function to filter a list of names to find all that sound similar to a given name.

<?php
   // List of Indian names
   $names = ["Suresh", "Sureesh", "Saurabh", "Sunil", "Suman"];

   // Name to compare
   $targetName = "Suresh";

   // Soundex key of the target name
   $targetSoundex = soundex($targetName);

   // Filter and show names with matching Soundex keys
   echo "Names sounding similar to '$targetName':\n";
   foreach ($names as $name) {
      if (soundex($name) === $targetSoundex) {
         echo "- $name\n";
      }
   }
?> 

Output

Following is the output of the above code −

Names sounding similar to 'Suresh':
- Suresh
- Sureesh