Commonly used string processing functions in PHP and how to use them

PHP is a server-side scripting language. As we all know, string is the most basic data type in any programming language. There are many string processing functions in PHP. How to use these functions flexibly is very critical for developing efficient and standardized programs. This article will introduce the commonly used string processing functions in PHP and how to use them.

1. String length processing

1. strlen function

strlen function returns the length of a string. This function does not count multi-byte characters. Instead, only single-byte characters are counted.

For example:

$str = "hello world";
echo strlen($str);         // 输出11
$str = "你好，世界";
echo strlen($str);         // 输出13

2. mb_strlen function

mb_strlen function returns the length of a multi-byte string. This function calculates the length of a multi-byte character. Encoding can also be specified. If the string contains Chinese characters, this function must be used to obtain the string length.

For example:

$str = "hello world";
echo mb_strlen($str);         // 输出 11

$str = "你好，世界";
echo mb_strlen($str, 'utf-8');  // 输出 4

2. String interception processing

1. substr function

The substr function is used to obtain the substring of a string. string. The substr function has three parameters:

The first parameter is the original string,

The second parameter is the starting position,

The third parameter is the interception length.

For example:

$str = "hello world";
echo substr($str, 0, 5);     // 输出 hello

$str = "你好，世界";
echo substr($str, 0, 3);     // 输出 你好

2. mb_substr function

Similar to mb_strlen, mb_substr is used to obtain the substring of a multi-byte string. The mb_substr function has three parameters:

The first parameter is the original string,

The second parameter is the starting position,

The third parameter is the interception length.

Similarly, if the string contains Chinese characters, this function must be used to obtain the intercepted string.

For example:

$str = "hello world";
echo mb_substr($str, 0, 5);     // 输出 hello

$str = "你好，世界";
echo mb_substr($str, 0, 3);     // 输出 你好

3. String replacement processing

1. str_replace function

str_replace function is used to replace the Replace a certain part with a new string. This function has three parameters:

The first parameter is the string to be replaced,

The second parameter is the new string to be replaced,

The third parameter Each parameter is a raw string.

For example:

$str = "hello world";
$newStr = str_replace('hello', 'hi', $str);
echo $newStr;                // 输出 hi world

$str = "Hello world";
$newStr = str_replace('Hello', 'hi', $str);
echo $newStr;                // 输出 hi world

If you need to replace text that is case-sensitive, use the str_ireplace function.

2. preg_replace function

The preg_replace function is used to replace a certain part of the string with a new string, but regular expressions can be used for matching. This function has three parameters:

The first parameter is a regular expression,

The second parameter is the new string to be replaced,

The third parameter is a raw string.

For example:

$str = "hello world";
$newStr = preg_replace('/hello/', 'hi', $str);
echo $newStr;                // 输出 hi world

$str = "Hello world";
$newStr = preg_replace('/hello/i', 'hi', $str);
echo $newStr;                // 输出 hi world

4. String segmentation processing

1. explode function

Theexplode function is used to split the string into the specified separator to separate. This function has two parameters:

The first parameter is the separator,

The second parameter is the original string.

For example:

$str = "hello world";
$arr = explode(' ', $str);
print_r($arr);               // 输出 Array ( [0] => hello [1] => world )

$str = "1,2,3,4,5";
$arr = explode(',', $str);
print_r($arr);               // 输出 Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 5 )

2. implode function

The implode function is used to concatenate array elements into strings. This function has two parameters:

The first parameter is the connector,

The second parameter is the array to be connected.

For example:

$arr = array('hello', 'world');
$str = implode(' ', $arr);
echo $str;                   // 输出 hello world

$arr = array(1,2,3,4,5);
$str = implode(',', $arr);
echo $str;                   // 输出 1,2,3,4,5

5. String formatting processing

1. strtolower function

strtolower function is used to convert strings in lowercase form.

For example:

$str = "HELLO WORLD";
$newStr = strtolower($str);
echo $newStr;                // 输出 hello world

2. strtoupper function

The strtoupper function is used to convert a string to uppercase.

For example:

$str = "hello world";
$newStr = strtoupper($str);
echo $newStr;                // 输出 HELLO WORLD

3. ucfirst function

The ucfirst function is used to convert the first character to uppercase.

For example:

$str = "hello world";
$newStr = ucfirst($str);
echo $newStr;                // 输出 Hello world

4. ucwords function

The ucwords function is used to convert the first character of each word to uppercase.

For example:

$str = "hello world";
$newStr = ucwords($str);
echo $newStr;                // 输出 Hello World

6. String comparison processing

1. strcmp function

strcmp function compares two strings and Return the difference between them. If they are equal, 0 is returned.

For example:

$str1 = "hello";
$str2 = "world";
echo strcmp($str1, $str2);   // 输出 -15

2. strcasecmp function

The strcasecmp function compares two strings, ignoring case, and returns the difference between them. If they are equal, 0 is returned.

For example:

$str1 = "hello";
$str2 = "WORLD";
echo strcasecmp($str1, $str2);  // 输出 0

The commonly used string processing functions in PHP are introduced here. These functions are very useful in daily development. Mastering these functions can improve our development efficiency.

Reference materials:

[PHP official documentation](http://www.php.net/)

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