Detailed explanation of PHP strpos() function usage

Detailed explanation of the usage of PHP strpos() function

In PHP programming, string processing is a very important part. PHP implements string processing by providing some built-in functions. Among them, the strpos() function is one of the most commonly used string functions in PHP. The purpose of this function is to search for the position of another specified string in a specified string, and return this position if it is contained, otherwise it returns false. This article will help you better understand and use this function through a detailed analysis of the usage of the PHP strpos() function.

1. Function syntax

strpos(string,find,start)

Parameter description:

1. string required. Specifies the string to be searched for.
2. find Required. Specifies the string to search for.
3. start Optional. Specifies where in the string to begin the search. The default is 0.

2. Function return value

The function returns an integer value or false. If the specified string is found in the string, the first occurrence of the string is returned. Position, starting from 0. If the specified string is not found, returns false. It should be noted that if the target string and the specified string are equal, the function returns 0 instead of false.

3. Example Demonstration

We illustrate the usage of this function through some specific examples, as follows:

Example 1: Find whether a string contains another character String

$str = "Hello world!";
if (strpos($str,"world") !== false)
{
echo "Found!";
}
else
{
echo "Not found!";
}
?>

Output result:

found it!

Example 2: Find the position where a string appears

echo strpos("Hello world!","world");
?>

Output result:

6

Example 3: Find the position where a string appears multiple times

$offset = 0 ;
$find = 'e';
$positions = array();
while(($pos = strpos($str, $find, $offset)) !== false) {

50815c3fb0c14b5263d594338f24f8f5

)

Example 4: Find the position where a string appears starting from the specified position

echo strpos("Hello world!","world",7);
?>

Output result:

-1

Example 5: Find whether a string is equal

if (strpos($str,"Hello world!") == 0)
{
echo "They are equal!";
}
else
{
echo "They are not equal !";
}
?>

Output result:

are equal!

4. Notes

1. This function is case-sensitive. If case-insensitive search is required, the stripos() function can be used instead.

2. If the specified string is empty, the function will return 0.

3. If the specified string is 0, the function will return the corresponding position.

4. If the length of the specified string is greater than the length of the search string, the function will return false.

5. If you need to determine whether the string is empty, you can use the empty() or strlen() function instead.

Summary:

This article introduces the usage of the PHP strpos() function in detail. Through the actual demonstration of this function, we can clearly understand the working principle of this function. It should be noted that the return value of this function may be false, so when using this function, you need to first determine whether its return value is false. This function is very useful during string processing.

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