How does php determine whether an array exists in a string?

With the development and progress of Internet technology, PHP, as a very popular scripting language, is widely used in Web development. In PHP development, the application of arrays is also very common. In actual development, it is often necessary to judge whether an array exists in a string. Then, this article will specifically introduce how to judge whether an array exists in a string in PHP.

First, the use of the in_array function in PHP

In PHP, a common way to judge whether an array exists in another array is to use the in_array () function. The in_array () function is used to determine whether a value is in the array, and returns true if it exists, and false if it does not exist. Its basic grammatical structure is as follows:

in_array( value, array, bool )

Where value represents the value to be searched, array represents the array to be searched, and bool represents whether strict mode is used, that is, whether the type is considered. Parameter bool is false by default, which means that the type is ignored. If bool is set to true, the types of value and array must be strictly matched.

Then, we can use the in_array () function to judge whether an array exists in a string. The basic code is as follows:

$arr = array("apple", "banana", "cherry");

$str = "I like apple pie.";

if (in_array($arr, $str)) {

echo "Match found.";

} else {

echo "Match not found.";

}

Among them, $arr array represents the array to find out whether it exists, and $str represents the string to find out. If any member of the array $arr is found in the string $str, it returns Match found. Otherwise, it returns Match not found.

Second, the use of strpos () function in PHP

In addition to the in_array () function, there is also a strpos () string function in PHP that can be used to determine whether an array exists in a string. The strpos () function is used to search for a specified character or string in a string. Its basic grammatical structure is as follows:

strpos( haystack, needle, offset )

Among them, haystack represents the string in which needle is searched, needle represents the string to be searched, and offset represents the position where the search is started. If needle is not found, it returns false；; Otherwise, the position of the character or substring in haystack is returned.

Then, we can use the strpos () function to determine whether an array exists in a string. The basic code is as follows:

$arr = array("apple", "banana", "cherry");

$str = "I like apple pie.";

foreach ($arr as $fruit) {

if (strpos($str, $fruit) ! == false) { echo "Match found."; break; }

}

Where $arr array represents the array to be searched, and $str represents the string to be searched. Use the foreach loop to traverse each member in the array $arr. In the loop, use the strpos () function to find out whether each member is in the string $str. If it is found, it will return to Match found and end the loop. Otherwise, continue the loop until it is found.

Third, the comparison of the two methods

Although both in_array () function and strpos () function can be used to judge whether an array exists in a string, there are still some differences between them. We compare the differences between them from the following aspects.

1. Usage is different from parameters.

The parameters of in_array () function include the value and array to be searched, while the parameters of strpos () function include the string and substring to be searched. Specifically, the in_array () function is similar to the array function, while the strpos () function belongs to the string function.

2. The case sensitivity of arrays and strings is different.

The in_array () function is case-insensitive by default, while the strpos () function is case-sensitive. If you want to set case sensitivity in the in_array () function, you need to set its third parameter to true.

3. Handling different cases for multiple matches.

If multiple matches are found in the string, the strpos () function only returns the position of the first match, while the in_array () function can return multiple matches.

IV. Conclusion

This paper mainly introduces two methods to judge whether an array exists in a string in PHP: in_array () function and strpos () function. Although these two methods have their own advantages and limitations, they can be used flexibly in actual development and choose the appropriate method according to specific scenarios. Either way, as long as it can help developers realize functions efficiently, it is a good method.