PHP string is a sequence of characters i.e., used to store and manipulate text. PHP supports only 256-character set and so that it does not offer native Unicode support. There are 4 ways to specify a string literal in PHP.
We can create a string in PHP by enclosing the text in a single-quote. It is the easiest way to specify string in PHP.
For specifying a literal single quote, escape it with a backslash (\) and to specify a literal backslash (\) use double backslash (\\). All the other instances with backslash such as \r or \n, will be output same as they specified instead of having any special meaning.
For Example
Following some examples are given to understand the single quoted PHP String in a better way:
Example 1
<?php
$str='Hello text within single quote';
echo $str;
?>Output:
We can store multiple line text, special characters, and escape sequences in a single-quoted PHP string.
Example 2
<?php $str1='Hello text multiple line text within single quoted string'; $str2='Using double "quote" directly inside single quoted string'; $str3='Using escape sequences \n in single quoted string'; echo "$str1 <br/> $str2 <br/> $str3"; ?>
Output:
Example 3
<?php $num1=10; $str1='trying variable $num1'; $str2='trying backslash n and backslash t inside single quoted string \n \t'; $str3='Using single quote \'my quote\' and \\backslash'; echo "$str1 <br/> $str2 <br/> $str3"; ?>
Output:
In PHP, we can specify string through enclosing text within double quote also. But escape sequences and variables will be interpreted using double quote PHP strings.
Example 1
<?php $str="Hello text within double quote"; echo $str; ?>
Output:
Now, you can't use double quote directly inside double quoted string.
Example 2
<?php $str1="Using double "quote" directly inside double quoted string"; echo $str1; ?>
Output:
We can store multiple line text, special characters and escape sequences in a double quoted PHP string.
Example 3
<?php $str1="Hello text multiple line text within double quoted string"; $str2="Using double \"quote\" with backslash inside double quoted string"; $str3="Using escape sequences \n in double quoted string"; echo "$str1 <br/> $str2 <br/> $str3"; ?>
Output:
In double quoted strings, variable will be interpreted.
Example 4
<?php $num1=10; echo "Number is: $num1"; ?>
Output:
Heredoc syntax (<<<) is the third way to delimit strings. In Heredoc syntax, an identifier is provided after this heredoc <<< operator, and immediately a new line is started to write any text. To close the quotation, the string follows itself and then again that same identifier is provided. That closing identifier must begin from the new line without any whitespace or tab.
The identifier should follow the naming rule that it must contain only alphanumeric characters and underscores, and must start with an underscore or a non-digit character.
Valid Example
<?php
$str = <<<Demo
It is a valid example
Demo; //Valid code as whitespace or tab is not valid before closing identifier
echo $str;
?>Output:
Invalid Example
We cannot use any whitespace or tab before and after the identifier and semicolon, which means identifier must not be indented. The identifier must begin from the new line.
<?php
$str = <<<Demo
It is Invalid example
Demo; //Invalid code as whitespace or tab is not valid before closing identifier
echo $str;
?>This code will generate an error.
Output:
Heredoc is similar to the double-quoted string, without the double quote, means that quote in a heredoc are not required. It can also print the variable's value.
Example
<?php $city = 'Delhi'; $str = <<<DEMO Hello! My name is Misthi, and I live in $city. DEMO; echo $str; ?>
Output:
Example
We can add multiple lines of text here between heredoc syntax.
<?php $str = <<<DEMO It is the example of multiple lines of text. DEMO; echo $str; echo '</br>'; echo <<<DEMO // Here we are not storing string content in variable str. It is the example of multiple lines of text. DEMO; ?>
Output:
Below are the example with class and their variable
Example
<?php
class heredocExample{
var $demo;
var $example;
function __construct()
{
$this->demo = 'DEMO';
$this->example = array('Example1', 'Example2', 'Example3');
}
}
$heredocExample = new heredocExample();
$name = 'Gunjan';
echo <<<ECO
My name is "$name". I am printing some $heredocExample->demo example.
Now, I am printing {$heredocExample->example[1]}.
It will print a capital 'A': \x41
ECO;
?>Output:
Newdoc is similar to the heredoc, but in newdoc parsing is not done. It is also identified with three less than symbols <<< followed by an identifier. But here identifier is enclosed in single-quote, e.g. <<<'EXP'. Newdoc follows the same rule as heredocs.
The difference between newdoc and heredoc is that - Newdoc is a single-quoted string whereas heredoc is a double-quoted string.
Example-1:
<?php
$str = <<<'DEMO'
Welcome to rookienerd.
Learn with newdoc example.
DEMO;
echo $str;
echo '</br>';
echo <<< 'Demo' // Here we are not storing string content in variable str.
Welcome to rookienerd.
Learn with newdoc example.
Demo;
?>Output:
Go to view page source and see the source of the program.
Example
The below example shows that newdoc does not print the variable's value.
<?php
class heredocExample{
var $demo;
var $example;
function __construct()
{
$this->demo = 'DEMO';
$this->example = array('Example1', 'Example2', 'Example3');
}
}
$heredocExample = new heredocExample();
$name = 'Gunjan';
echo <<<ECO
My name is "$name". I am printing some $heredocExample->demo example.
Now, I am printing {$heredocExample->example[1]}.
It will print a capital 'A': \x41
ECO;
?>Output:
The output of the above program will be like:
Invalid Example
We cannot use any whitespace or tab before and after the identifier and semicolon, means identifier must not be indented. The identifier must begin from the new line. It is also invalid in newdoc same as heredoc.
<?php
$str = <<<'Demo'
It is Invalid example
Demo; //Invalid code as whitespace or tab is not valid before closing identifier
echo $str;
?>This code will generate an error.
Output:
