The PHP Function Is_string()

A string is a data type that contains text

The is_string() PHP function is used to check if a type of variable is a string. A string is a data type, such as floating point or integer, but it represents text rather than numbers. A string uses a set of characters that includes spaces and numbers. For instance, an address such as "1234 Broadway" and the sentence "I ate 3 hotdogs" contain numbers but they should be treated as text, not as numbers.

 

Is_string is used within an if () statement to treat strings in one way and non-strings in another. It returns true or false. For example:

 <?php 
 if (is_string(23)) 
 {
 echo "Yes";
 } else {
 echo "No";
 }
 ?>
 
The code above should output "No" because 23 is not a string. Let's try this again:
 <?php 
 if (is_string("Hello World")) 
 {
 echo "Yes";
 } else {
 echo "No";
 }
 ?>
 

Since "Hello World" is a string, this would echo "Yes."​​

Specifying a String

A string can be specified in four ways:

  • Single quoted
  • Double quoted  
  • Heredoc syntax
  • Nowdoc Syntax

Each of these methods requires strict adherence to PHP rules, which are available at the PHP website. The simplest method, single quoted strings, requires special treatment when literal single quotation marks or literal backslashes appear in the string. Include a backslash in front of the single quotation mark or backslash within the string.

The example below illustrates this treatment:

<?php

// Outputs: Arnold said: "I'll be back"

echo 'Arnold said: "I\'ll be back"';

 

// Outputs: I deleted C:\*.*?

echo 'I deleted C:\\*.*?';

?>

Similar Functions

  • is_float() - determines if the type of variable is float
  • is_int() - determines if the type of variable is integer
  • is_bool() - determines if a variable is a boolean
  • is_object() - determines if a variable is an object
  • is_array() - determines is a variable is an array