How to Check if a PHP String Contains Another?

In most object-oriented languages, you will need to check if a string contains another string, a substring, or a character.This is a common question asking you to check whether a PHP string contains another string in a programming interview. Many armature programmers may think that checking for the existence of a string in another string is very challenging, but truth be told. Checking if a string contains substring is one of the easiest tasks in programming. This article will comprehensively describe how to check if a PHP string contains a substring or another string.

How to Check If A PHP String Contains another String

There are several ways to verify if a PHP string contains another string. You can use these string functions to know if a PHP string contains substring or a character:

  1. strstr – this function is used to return the first occurrence of a string in a PHP string. The strstr( ) function uses the following syntax to enable PHP to find a string in another string:
    char * strstr ( const char *, const char * );
    char * strstr ( char * str1, const char * str2 );
  2. stristr – the stristr function is similar to the strstr one, only that it is case-insensitive. It locates a pointer to the first occurrence without considering case sensitivity.
  3. strrchr – this C library function searches for the last occurrence of c (the character) in a string. The syntax for this function is char *strrchr(const char *str, int character);
  4. strpos – the strpos() function returns the position of the first occurrence of a string in another string. This function is commonly used as it is the easiest method to assist PHP find string in string.
  5. strpbrk – this is another inbuilt string function that returns a string from a character identical to any character specified in a PHP string. This function uses the syntax char *strpbrk(const char *s1, const char *s2).


In our example, we will use the strpos() function technique to find whether a PHP string contains another string. This approach is mostly preferred because it is faster and demands less memory.
Assumptions: Let’s assume we have one string called $flashlight and another string called $flash. This is how the strpos function will work:

The following code is used when dealing with the strstr() function technique:

int main()
const char flashlight [20] = “TutorialsPoint”;
const char flash[10] = “Point”;
char *ret;

ret = strstr(flashlight, flash);

printf(“The substring is: %s\n”, ret);


Keep in mind that the strstr() function is case-sensitive so you would want to use the stristr() function when performing a case-insensitive search. However, you can wrap your strings with the strtolower() function as it converts the strings into lower case which assists in eliminating problems that come with a case-sensitive string.

Recommended read: since you’re here, you might also be interested in our collection of 14 PHP interview questions!


In a PHP if string contains string, you can find that out by using the strpos() function. Alternatively, you can use the strstr() function if the string contains a case-sensitive character and the stristr() function for a case-insensitive search. We hope that this article helps you check for a string or substring in a PHP string. Feel free to give any suggestions or ask questions about this article in our discussion forum.