How to delete specified characters at the beginning of a string in php

When using PHP for string operations, it is often necessary to delete some specified characters or strings at the beginning of the string. PHP provides a variety of methods to remove characters or strings at the beginning of a string. This article will introduce you to some common methods.

Method 1: Use the substr function

The substr function can intercept a substring in the string, thereby achieving the effect of deleting the specified string at the beginning of the string. The specific code is as follows:

$str = "hello world";
$remove = "hello";
if(substr($str, 0, strlen($remove)) == $remove){
    $str = substr($str, strlen($remove));
}
echo $str;

Code analysis: We first define a string $str and the specified string that needs to be deleted $remove, and then use the substr function to The string is intercepted, starting from the first position (subscript 0) to the length of the string to be deleted, and then judging whether the intercepted string is equal to the string to be deleted, if equal, the original string is removed from the string to be deleted. Start intercepting the position after deleting the string, and finally output the string.

Method 2: Use the preg_replace function

preg_replace is a commonly used string replacement function in PHP, which can support regular expressions. We can use it to remove the specified character or string at the beginning of the string. The specific code is as follows:

$str = "hello world";
$remove = "hello";
$str = preg_replace('/^' . preg_quote($remove, '/') . '/', '', $str);
echo $str;

Code analysis: The preg_quote function is used to escape regular expression metacharacters in strings to prevent them from being interpreted as regular expressions. Next, we include the string we want to delete at the beginning of the regular expression and use the ^ symbol to indicate that the string only appears at the beginning of the string. Finally, we replace the part obtained by match with the empty string and output the string.

Method 3: Use the ltrim function

The ltrim function can delete the specified character or string at the beginning of the string. Its usage is very simple. The specific code is as follows:

$str = "hello world";
$remove = "hello";
$str = ltrim($str,$remove);
echo $str;

Code analysis: The ltrim function accepts two parameters. The first parameter is the character or string to be deleted, and the second parameter is the string to be deleted. . When the first parameter is a string, each character will be deleted. When the second parameter is not specified, all whitespace characters will be deleted. Finally, the deleted string is output.

Summary

The above are three commonly used methods to delete specified characters or strings at the beginning of strings. These methods can effectively help us perform string operations. Just choose the appropriate method according to actual needs.

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