Use the PHP function 'substr' to return the substring of a string

Use PHP function "substr" to return a substring of a string

In PHP, we often need to perform some operations on strings, such as intercepting part of a string. At this time, we can use PHP's built-in function "substr" to achieve this function. The substr function returns a substring of a string based on the specified starting position and length.

The following is a simple example that demonstrates how to use the substr function to intercept part of a string:

<?php
$str = "Hello World";
$substring = substr($str, 0, 5);
echo $substring; // 输出 "Hello"
?>

In the above code, we first define a string variable "$str" , its value is "Hello World". Then, we called the substr function to intercept the first 5 characters of the string and assigned the result to the variable "$substring". Finally, we use the echo statement to output the intercepted substring to the browser.

When using the substr function, you need to pass in three parameters. The first parameter is the string variable to be intercepted, the second parameter is to specify the position from which to intercept, and the third parameter is to specify the length of interception. In the above example, we set the starting position of the string to 0, which means intercepting from the first character of the string. Then, we set the intercepted length to 5, which means intercepting the first 5 characters of the string. If the third parameter is not specified, the substr function will intercept from the starting position to the end of the string.

In addition to intercepting the first n characters, we can also intercept any part of the string by setting the starting position and length. For example, if we want to intercept the 6th to 10th characters of the string, we can use the following code:

<?php
$str = "Hello World";
$substring = substr($str, 5, 5);
echo $substring; // 输出 " World"
?>

In the above code, we set the starting position to 5, which means starting from the 10th character of the string. Start intercepting after 6 characters. Then, we set the intercepted length to 5, which means intercepting the first 5 characters of the string.

It should be noted that the starting position of the substr function can be a negative number, indicating that counting starts from the end of the string. For example, if we want to intercept the last 3 characters of the string, we can use the following code:

<?php
$str = "Hello World";
$substring = substr($str, -3);
echo $substring; // 输出 "rld"
?>

In the above code, we did not specify the length of the interception, but only set the starting position to -3. In this way, the substr function will intercept from the third to last character of the string and continue to the end of the string.

In summary, the PHP function "substr" is a very useful string manipulation function that can intercept a part of a string based on the starting position and length. By setting parameters appropriately, we can achieve flexible operation and processing of strings. Hope the above example can help you.

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