A substring is a portion of a string. For example, "hello" is a substring of the string "Oh hello, how are you?" and "el" is a substring of the string "hello". Manipulating strings is very common in programming, and working with substrings is often necessary.

The substr_count() function returns the number of instances of a substring within a string. It takes two arguments, the string to search through—sometimes called the haystack— and the string to search for—sometimes called the needle.

$story = "I was like, \"Dude, like just tell me what you like think because like everyone else is like being totally honest, and like I just want to know what you like think.\" So like I don't know...";

echo substr_count($story, "like"); // Prints: 8

In the code above, we invoked the substr_count() function, passing in $story as the haystack and "like" as the needle. We used echo to print the returned result—8, which is the number of times the substring "like" appears in the $story string.

Let’s practice!