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Vijay Thapa
Vijay Thapa

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What Is The Difference Between Single and Double Quotes in PHP?

#webdev #php #programming #beginners

To assign string values in PHP, we use quotes. And we use single quotes and double quotes interchangeably as similar things until you get some error.
You’ll feel you’ve written the correct code after checking it multiple times and don’t know why it’s not working.
It’s frustrating, I know and have been there as well.

When are Single Quotes and Double Quotes used in PHP?

Simply, as told earlier quotes are used to assign string variables in PHP.
And if the string value has double quote (“”) on it, then single quotes is used to assign it to the variable.
For example

$variable1 = ‘This is a “GAME” changer’;
// Output: This is a GAME changer.
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Similarly, if the string value has a single quote (‘’) on it, then double quotes is used to assign it to the variable.
For example

$variable2 = “I’m Vijay.”;
// Output: I’m Vijay
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Escaping

If you don’t want to switch between Quotes (Single and Double), you can simply use escaping technique. Simply, escaping is ignoring a character and you can do it using backslash \ .
For example

$sentence = ‘I\’m Vijay.’;
// Output: I’m Vijay. 
// It simply ignores the single quote after I in the sentence.
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And here comes String Interpolation

Apart from generic uses of quotes in PHP, there’s a technique called String Interpolation where you can embed variable values on string which makes it easier to make dynamic texts.
And it can be easily performed with double quotes in PHP.
For example

$name = “Vijay”;
$sentence = “My name is $name”;
// Output: My name is Vijay
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Sometimes we forget and use single quotes while passing the variable which gives us an error with a headache as it’s a silly mistake and hard to spot.
For example

$name = “Vijay”;
$sentence = ‘My name is $name’;
// Output: My name is $name
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You can also perform string interpolation with single quotes using Concatenation technique. It is a technique of connecting two or more strings/variables. And it’s done with “.” (dot or fullstop) sign in PHP.
For example

$name = ‘Vijay Thapa’;
$sentence = ‘My name is ’.$name;
// Output: My name is Vijay Thapa
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So, the difference between single quote and double quote in PHP is subtle but important.

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Top comments (1)

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david duymelinck •

While string interpolation makes the double quoted string more versatile, it is not always the best solution.

If you move that string to a place that doesn't have the variable then it will generate an error.

$sentence = “My name is $name”;
$name = “Vijay”;
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You can only use the double quoted string with a variable a single time, while a string with a placeholder can be used multiple times.

$sentence = 'My name is %s';

echo sprintf($sentence, 'Vijay');
echo sprintf($sentence, 'David');
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The rule of thumb I use is think of strings as an immutable value. That makes them most of the time a part of the configuration instead of a part of the code.