PHP Strings
A string is a sequence of characters, like "Hello world!".
Strings
Strings in PHP are surrounded by either double quotation marks, or single quotation marks.
Example
echo "Hello";
echo 'Hello';
Note There is a big difference between double quotes and single quotes in PHP.
Double quotes process special characters, single quotes does not.
Double or Single Quotes?
You can use double or single quotes, but you should be aware of the differences between the two.
Double quoted strings perform action on special characters.
E.g. when there is a variable in the string, it returns the value of the variable:
Example
Double quoted string literals perform operations for special characters:
$x = "John";
echo "Hello $x";
Single quoted strings does not perform such actions, it returns the string like it was written, with the variable name:
Example
Single quoted string literals returns the string as it is:
$x = "John";
echo 'Hello $x';
String Length
The PHP strlen() function returns the length of a string.
Example
Return the length of the string "Hello world!":
echo strlen("Hello world!");
Word Count
The PHP str_word_count() function counts the number of words in a string.
Example
Count the number of word in the string "Hello world!":
echo str_word_count("Hello world!");
Search For Text Within a String
The PHP strpos() function searches for a specific text within a string.
If a match is found, the function returns the character position of the first match. If no match is found, it will return FALSE.
Example
Search for the text "world" in the string "Hello world!":
echo strpos("Hello world!", "world");
Tip: The first character position in a string is 0 (not 1).
Modify Strings
PHP has a set of built-in functions that you can use to modify strings.
Upper Case
Example
The strtoupper() function returns the string in upper case:
$x = "Hello World!";
echo strtoupper($x);
Lower Case
Example
The strtolower() function returns the string in lower case:
$x = "Hello World!";
echo strtolower($x);
Replace String
The PHP str_replace() function replaces some characters with some other characters in a string.
Example
Replace the text "World" with "Dolly":
$x = "Hello World!";
echo str_replace("World", "Dolly", $x);
Reverse a String
The PHP strrev() function reverses a string.
Example
Reverse the string "Hello World!":
$x = "Hello World!";
echo strrev($x);
Remove Whitespace
Whitespace is the space before and/or after the actual text, and very often you want to remove this space.
Example
The trim() removes any whitespace from the beginning or the end:
$x = " Hello World! ";
echo trim($x);
Convert String into Array
The PHP explode() function splits a string into an array.
The first parameter of the explode() function represents the "separator". The "separator" specifies where to split the string.
Note: The separator is required.
Example
Split the string into an array. Use the space character as separator:
$x = "Hello World!";
$y = explode(" ", $x);
//Use the print_r() function to display the result:
print_r($y);
/*
Result:
Array ( [0] => Hello [1] => World! )
*/
Concatenate Strings
String Concatenation
To concatenate, or combine, two strings you can use the . operator:
Example
$x = "Hello";
$y = "World";
$z = $x . $y;
echo $z;
The result of the example above is HelloWorld, without a space between the two words.
You can add a space character like this:
Example
$x = "Hello";
$y = "World";
$z = $x . " " . $y;
echo $z;
An easier and better way is by using the power of double quotes.
By surrounding the two variables in double quotes with a white space between them, the white space will also be present in the result:
Example
$x = "Hello";
$y = "World";
$z = "$x $y";
echo $z;
Slicing Strings
Slicing
You can return a range of characters by using the substr() function.
Specify the start index and the number of characters you want to return.
Example
Start the slice at index 6 and end the slice 5 positions later:
$x = "Hello World!";
echo substr($x, 6, 5);
Note The first character has index 0.
Slice to the End
By leaving out the length parameter, the range will go to the end:
Example
Start the slice at index 6 and go all the way to the end:
$x = "Hello World!";
echo substr($x, 6);
Slice From the End
Use negative indexes to start the slice from the end of the string:
Example
Get the 3 characters, starting from the "o" in world (index -5):
$x = "Hello World!";
echo substr($x, -5, 3);
Note The last character has index -1.
Negative Length
Use negative length to specify how many characters to omit, starting from the end of the string:
Example
From the string "Hi, how are you?", get the characters starting from index 5, and continue until you reach the 3. character from the end (index -3).
Should end up with "ow are y":
$x = "Hi, how are you?";
echo substr($x, 5, -3);
Escape Character
To insert characters that are illegal in a string, use an escape character.
An escape character is a backslash \ followed by the character you want to insert.
An example of an illegal character is a double quote inside a string that is surrounded by double quotes:
Example
$x = "We are the so-called "Vikings" from the north.";
To fix this problem, use the escape character \":
Example
$x = "We are the so-called \"Vikings\" from the north.";
Escape Characters
Other escape characters used in PHP:
| Code | Result |
|---|---|
| \' | Single Quote |
| \" | Double Quote |
| \$ | PHP variables |
| \n | New Line |
| \r | Carriage Return |
| \t | Tab |
| \f | Form Feed |
| \ooo | Octal value |
| \xhh | Hex value |