Detailed explanation on the use of strchr, str_replace and strpos functions

In PHP programming, string processing is relatively common, and operations such as search and replacement of strings are often required. In string processing, it is more common to use strchr, str_replace, and strpos functions. Next, let’s explain the use of these three functions in detail.

1. strchr function

The strchr function searches for the specified character in a string and returns the string from the specified character to the end of the string. The syntax is as follows:

strchr(string,char,part) 

Among them, the parameter string is the original string to be searched, the parameter char is the character specified to be searched, and the parameter part is an optional parameter used to specify the position from which to start searching.

For example, the following code will find the string after the comma "," in the string "Hello, world!":

<?php
$str = "Hello, world!";
echo strchr($str,","); // 输出 ", world!"
?>

Of course, we can also use the third parameter part to specify Starting position of search:

<?php
$str = "Hello, world!";
echo strchr($str,",", true); // 输出 "Hello"
?>

It should be noted that the strchr function is case-sensitive. If it is not case sensitive, we can use stristr function.

2. str_replace function

The str_replace function is used to find and replace the specified substring in a string. The syntax is as follows:

str_replace(search,replace,string,count)

Among them, the search parameter is the character (string) that needs to be replaced, the replace parameter is the character (string) used to replace, the string parameter is the original string that needs to be replaced, and count The parameter is an optional parameter used to specify the number of replacements. The default is to replace all.

For example, in the following code, all "world" will be replaced with "PHP":

<?php
$str = "Hello, world! I love world!";
echo str_replace("world", "PHP", $str); 
// 输出 "Hello, PHP! I love PHP!"
?>

It should be noted that this function is also case-sensitive. If it is not case sensitive, we can use str_ireplace function.

3. strpos function

The strpos function is used to find the specified character or substring in a string and return the position of the first matching character. The syntax is as follows:

strpos(string,search,start)

Among them, the parameter string is the original string that needs to be searched, the search parameter is the character (string) to be searched, and the start parameter is an optional parameter used to specify the starting position. search. If no matching character is found, the function will return false.

For example, in the following code, we will find "world" in the string "Hello, world!" and return the location:

<?php
$str = "Hello, world!";
echo strpos($str, "world"); // 输出 "7"
?>

It should be noted that this function is case-sensitive. If it is not case sensitive, we can use stripos function.

Summary:

The strchr, str_replace, and strpos functions are commonly used string processing functions in PHP programming. It is very important for developers to master the use of these three functions. I hope the above content will be helpful to your programming practice.

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