PHP retrieval string function instance usage

In the PHP language, many functions are provided that can be used to retrieve strings, so that PHP can also implement the search function for strings like word. This will be very convenient to use, and you can easily find the content you want to find, keywords, statistical times and other related things. Let’s explain the commonly used retrieval functions of two strings.

1. Use the strstr() function to find the specified keyword

The meaning of the strstr() function is to get a specified string in another A substring from the first occurrence of a string to the end of the latter. If the execution is successful, the obtained substring (matching characters exist) is returned; if it fails, false is returned.

Its syntax format is as follows:

strstr(haystack,needle)

Its parameter description is as follows:

Parameter Number	Description
haystack	Required parameters, specify which string to search from
needle	Required parameters, specify the search object. If the parameter is a numeric value, then the character that matches the ASCII value of this value will be searched

Note: This function is case-sensitive.

Use the strstr() function to obtain the suffix name of the image, and determine whether the format of the obtained suffix name is correct. The sample code is as follows:

<?php
 $picture = "123.jpg";
 $picture_name = strstr($picture,".");      // 通过strstr()函数获取图片的后缀
 echo $picture_name;
 echo "<br>";
 if($picture_name != ".jpg"){               // 根据获取的图片后缀判断格式是否正确
   echo "图片格式不正确！";
 }else{
   echo "正确的图片格式";
 }
?>

The above code will output:

.jpg
正确的图片格式

If you need to perform a case-insensitive search, please use the stristr() function.

2. Use the substr_count() function to retrieve the number of occurrences of a substring

The substr_count() function refers to getting the specified character in a string The number of occurrences. Its syntax is as follows:

substr_count(haystack,needle)

The parameter haystack is the specified string; the parameter needle is the specified character.

Use the substr_count() function to get the number of times a substring appears in a string. The example code is as follows:

<?php
 $str = "PHP中文网";
 echo substr_count($str,"P");   //输出查询的字符串
?>

The output result is:

2

Note: Retrieve substrings The number of occurrences is generally used in search engines to count the number of times a substring appears in a string, so that users can immediately grasp the number of times a substring appears in a string.

Of course, there are other ways to retrieve strings in PHP. Here we just explain a few simple methods. Friends can continue to learn more course content on the PHP Chinese website.

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