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simon
Asked: 2020-07-21 09:39:35 +0800 CST 2020-07-21 09:39:35 +0800 CST

What is the functionality of String double quoted in PHP?

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While reading a PHP article, I saw the type of string php double quotedand was curious to know how it works while reading their English documentation on PHP.

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I didn't find much information about it, String double quotedis it just a Stringsimple and ordinary one or does it have any special or additional functionality?

php

2 Answers

  1. Best Answer

    The difference between one stringwrapped in single quotes and one wrapped in double quotes is that the one with single quotes will always be interpreted as a literal and the one with double quotes will first be checked by the interpreter to check whether or not it should interpret something in its interior.

    This may sound somewhat confusing but with an example it will be much clearer:

    Use of single quotes

    $nombre = 'Pepe';

echo 'Mi nombre es $nombre';

    Result:

    my name is $name

    Use of double quotes

    $nombre = 'Pepe';

echo "Mi nombre es $nombre";

    my name is pepe

    As you can see, with the use of single quotes the interpreter understands that there is nothing within them that must be interpreted, so the name of the variable is literally written as if it were one more word.

    In the case of doubles, it does check what is inside, finding the variable $nombreand obtaining its value.

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  2. Reviewing the link you provide in your same question, there are 2 main scenarios (although they are not the only ones)

    Scenario 1

    What is written inside single quotes and is dynamic, for example:

    • line breaks
    • variables
    • constants

    it will be interpreted literally, that is, there will be no interpolation of the data and interpretation of the line break symbol, for example.

    Example scenario 1

    The following script is run from the console and behaves as follows:

    1. I declare a variable that contains the age, like this:$edad = 20
    $edad = 23;
    1. We print said variable inside a statement echo, trying to apply a line break to it as follows:
    php > $edad = 23;
php > echo 'Tu edad es \n $edad';
Tu edad es \n $name

    As you can see, there is no interpretation of the content of the variable, so it does not interpolate it and it does not apply the line break either.

    scenario 2

    From the documentation:

    When a string is specified in double quotes or with heredoc, variables are parsed within it.

    Which could be translated as:

    When a string is specified in double quotes or with heredoc, the variables are parsed into it:

    • line breaks
    • variables
    • constants

    it is interpolated or interpreted dynamically, displaying it in the output printed from the console or from the browser.

    Example scenario 2

    Repeating the same exercise of scenario 1, we obtain the following:

    php > $edad = 20;
php > echo "Tu edad es \n $edad";
Tu edad es
 20

    Extra

    You can also within a print of values, enclose a variable inside {}but there must not be empty spaces between them and the variable to be interpolated.

    php > $edad = 20;
php > echo "Tu edad es \n {$edad}";
Tu edad es
 20

    What about the values CONSTANTES?

    Unlike variables, constants do not have a symbol that the PHP interpreter can take as a reference to carry out the interpolation process and print the associated value.

    Example

    php > DEFINE('INCREMENTO', 20);
php > echo "El valor del incremento es de: INCREMENTO";
El valor del incremento es de: INCREMENTO

    As can be seen, the value of the constant is not interpreted and it only prints its name literally, so in order to achieve the above we can, for example, do a concatenation process:

    Option 1

    DEFINE('INCREMENTO', 20);
echo "El incremento es de: ".INCREMENTO;

    Giving an output like this:

    El incremento es de: 20

    Option 2

    According to the PHP documentation , we can use the method sprintfwhich returns a string formatted as follows:

    DEFINE('INCREMENTO', 20);    
$cadena = "El valor de incremento es de: \n %d";    
echo sprintf($cadena, INCREMENTO);

    Getting an output like this:

    El valor de incremento es de: 
20

    Where, as can be seen, the line break is interpreted and the constant would remain within the original text string.

    References

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