PHP – mb_eregi() function

The mb_eregi() function in PHP performs case-insensitive regular expression matching with multibyte support. Unlike mb_ereg(), it ignores case when comparing patterns, making it useful for international text processing.

Syntax

int mb_eregi(
   string $pattern,
   string $string,
   array &$matches = null
)

Parameters

• pattern − The regular expression pattern to match (case-insensitive)

• string − The input string to search within

• matches − Optional array to store matched substrings. If matches are found, they are stored in this array

Return Value

Returns the number of bytes of the matched string if successful, or FALSE if no match is found.

Example 1: Basic Case-Insensitive Matching

This example demonstrates case-insensitive pattern matching −

<?php
   // Set UTF-8 encoding for multibyte support
   mb_regex_encoding("UTF-8");
   
   // Case-insensitive search for "WORLD"
   $result1 = mb_eregi("WORLD", "Hello World");
   echo "Pattern 'WORLD' found: " . ($result1 ? "Yes" : "No") . "<br>";
   
   // Case-insensitive search for "hello"  
   $result2 = mb_eregi("hello", "Hello World");
   echo "Pattern 'hello' found: " . ($result2 ? "Yes" : "No") . "<br>";
   
   // Pattern not found
   $result3 = mb_eregi("xyz", "Hello World");
   echo "Pattern 'xyz' found: " . ($result3 ? "Yes" : "No");
?>

Pattern 'WORLD' found: Yes
Pattern 'hello' found: Yes
Pattern 'xyz' found: No

Example 2: Using Matches Array

This example shows how to capture matched substrings −

<?php
   mb_regex_encoding("UTF-8");
   
   $text = "Contact us at SUPPORT@EXAMPLE.COM";
   $pattern = "([a-z]+)@([a-z]+\.[a-z]+)";
   
   $result = mb_eregi($pattern, $text, $matches);
   
   if ($result) {
       echo "Full match: " . $matches[0] . "<br>";
       echo "Username: " . $matches[1] . "<br>";
       echo "Domain: " . $matches[2];
   } else {
       echo "No email found";
   }
?>

Full match: SUPPORT@EXAMPLE.COM
Username: SUPPORT
Domain: EXAMPLE.COM

Comparison: mb_eregi() vs mb_ereg()

Conclusion

The mb_eregi() function is essential for case-insensitive pattern matching in multibyte strings. It's particularly useful when working with user input or international text where case variations need to be ignored.