To extract substrings from PHP strings, you can use the substr() function, which is syntax substr(string $string, int $start, ?int $length = null), and if the length is not specified, it will be intercepted to the end; when processing multi-byte characters such as Chinese, you should use the mb_substr() function to avoid garbled code; if you need to intercept the string according to a specific separator, you can use exploit() or combine strpos() and substr() to implement it, such as extracting file name extensions or domain names.
Want to extract substrings from PHP strings? In fact, the method is quite direct, the key is to use the right function. PHP provides several common functions to handle string interception, the most common one is substr() , which can meet most needs.
Use the substr() function to extract substrings
This is the most commonly used method of string interception. The basic syntax is:
substr(string $string, int $start, ?int $length = null)
-
$startis the starting position (starting from 0) -
$lengthis an optional parameter indicating how many characters to be intercepted
For example:
$str = "Hello, world!"; echo substr($str, 7, 5); // Output "world"
If you do not specify $length , you will be intercepted from the start position to the end:
echo substr($str, 7); // Output "world!"
Note: If the starting position exceeds the length of the string, false will be returned; negative numbers will indicate the number from behind to front.
When processing multi-byte characters such as Chinese, use mb_substr()
If you are dealing with Chinese, Japanese or other non-ASCII characters, using substr() directly may cause garbled code. At this time, mb_substr() should be used, which is a multibyte-safe version.
mb_substr(string $str, int $start, ?int $length = null, string $encoding = 'utf-8')
Example:
$chinese = "Hello, world!"; echo mb_substr($chinese, 3, 2, 'UTF-8'); // Output "world"
This function is very practical when dealing with multilingual content and is recommended to use it first.
Intercept strings based on specific separators
Sometimes you want to intercept some content based on a certain character, such as taking a domain name from a URL, or splitting file name and extension. At this time, you can use explode() or strpos() substr() ) to combine it.
For example, take the extension from the file name:
$filename = "example.txt"; $parts = exploit('.', $filename); echo end($parts); // Output "txt"
Or you just want to get the content before the first point:
$pos = strpos($filename, '.');
if ($pos !== false) {
echo substr($filename, 0, $pos); // Output "example"
}This method is suitable for cutting strings according to rules, especially for formatted inputs such as paths, URLs, CSV data.
Basically that's it. PHP's string processing function is very flexible, the key is to select the appropriate function according to different scenarios. If you master the two functions like substr() and mb_substr() , you can handle most of the situations. If there is a specific delimiter, you can do it by combining explode() or searching functions.
The above is the detailed content of PHP get substring from a string. For more information, please follow other related articles on the PHP Chinese website!
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