php hides some characters

In PHP development, you may encounter the need to hide some characters. For example, when displaying an ID card number or mobile phone number, you need to hide part of the middle digits. This article will introduce several commonly used methods of hiding some characters in PHP.

1. substr_replace() function

The substr_replace function is used to replace part of the string. We can use this function to hide some characters that need to be hidden. The specific usage is as follows:

$str = '13812345678';
$hideStr = substr_replace($str, '****', 3, 4);
echo $hideStr; //输出：138****5678

In the above example, we hide the 4th to 7th digits in the mobile phone number 13812345678 and replace it with "**". Among them, the second parameter is the string to be replaced, the third parameter is the starting position of replacement, counting from 0, and the fourth parameter is the length of replacement. The position and value of parameters can be adjusted according to needs.

2. str_pad() function

The str_pad function is used to fill a string of specified length. We can use this function to intercept part of the string and replace it with a fixed-length hidden symbol, and then concatenate it with another part of the string. The specific usage is as follows:

$str = '110101199001011234';
$hideChar = '*';
$startPos = 6;
$replaceLen = 8;
$hideStr = str_pad('', $replaceLen, $hideChar);
$part1 = substr($str, 0, $startPos);
$part2 = substr($str, $startPos + $replaceLen);
$hidePart = $part1 . $hideStr . $part2;
echo $hidePart; //输出：110101********34

The above code hides the 7th to 14th digits in the ID number 110101199001011234 and replaces it with "*". Among them, the second parameter is the length of the hidden string, the third parameter is the hidden characters, and the fourth parameter is the length of the string that needs to be hidden. We adjust it as needed, and finally output the hidden ID number.

3. Regular expression replacement

Regular expressions are also tools commonly used for string matching and replacement in PHP. We can also use regular expressions to hide strings. The specific usage is as follows:

$str = '13812345678';
$hideStr = preg_replace('/\d(?=\d{4})/', '*', $str);
echo $hideStr; //输出：138****5678

In the above example, we used regular expressions to find the 2nd to 5th digits in the mobile phone number and replaced them with the "*" symbol. Among them, the number represented in the regular expression is \d, (?=\d{4}) means that the number must be followed by four digits. Here we use the zero-width positive prediction of the regular expression, so that a gap can be reserved in front of the matched number for filling of hidden symbols.

Summary

This article introduces three commonly used methods of hiding some characters in PHP, namely substr_replace function, str_pad function and regular expression replacement. Each method has its own characteristics and applicable scenarios, and you can choose according to actual needs. In actual development, we can use corresponding methods to hide based on actual business needs and security considerations.

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