Masking Chinese Mobile Numbers in PHP Using substr_replace, preg_replace, and substr

The article addresses the common need to hide personal phone numbers in applications and provides three PHP‑based techniques for masking an 11‑digit Chinese mobile number.

Method 1: Using substr_replace

# substr_replace — Replace part of a string
# Usage
substr_replace ( mixed $string , mixed $replacement , mixed $start , mixed $length = ? ) : mixed
# $string: original string
# $replacement: replacement string
# $start: start position (negative values count from the end)
# $length: length to replace (negative values also count from $start)
# Example
$mobile = '18512341234';
echo substr_replace($mobile, '****', 3, 4); // 185****1234
echo substr_replace($mobile, '****', -8, -4); // 185****1234

Method 2: Using regular expressions with preg_replace

# preg_replace — Perform a regular expression search and replace
# Usage
preg_replace ( mixed $pattern , mixed $replacement , mixed $subject , int $limit = -1 , int &$count = ? ) : mixed
# Example
$pattern = '/(\d{3})\d{4}(\d{4})/';
$new_mobile = preg_replace($pattern, '$1****$2', $mobile);
echo $new_mobile; // 185****1234

Method 3: Using substr to concatenate parts

# substr — Return part of a string
# Usage
substr ( string $string , int $start , int $length = ? ) : string
# Example
echo substr($mobile, 0, 3) . '****' . substr($mobile, 7, 4); // 185****1234
echo substr($mobile, 0, 3) . '****' . substr($mobile, -4, 4); // 185****1234

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