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Unit 5: Strings

Unlike in some shell environments in PHP, strings are not repeatedly processed for interpolation. Notes
Instead, any interpolations in a double-quoted string are processed, then the result is used as the
value of the string:

$bar = ‘this is not printed’; $foo = ‘$bar’; // single quotes print(“$foo”); $bar
5.1.2 Single-Quoted Strings

Single-quoted strings do not interpolate variables. Thus, the variable name in the following string
is not expanded because the string literal in which it occurs is single-quoted:

$name = ‘Pradip’; $str = ‘Hi, $navneet’; // single-quoted echo $str; Hi, $Navneet
The only escape sequences that work in single-quoted strings are \’, which puts a single quote
in a single-quoted string, and \\, which puts a backslash in a single-quoted string. Any other
occurrence of a backslash is interpreted simply as a backslash:
$name = ‘Tim O\’Reilly’; // escaped single quote echo $name; $path = ‘C:\\WINDOWS’; //
escaped backslash echo $path; $nope = ‘\n’; // not an escape echo $nope; Tim O’Reilly
C:\WINDOWS \n

<?php
echo ‘this is a simple string’;
echo ‘You can also have embedded newlines in

strings this way as it is
okay to do’;
// Outputs: Arnold once said: “I will be back”
echo ‘Arnold once said: “I\ will be back”’;

// Outputs: You deleted C:\*.*?
echo ‘You deleted C:\\*.*?’;

// Outputs: You deleted C:\*.*?
echo ‘You deleted C:\*.*?’;
// Outputs: This will not expand: \n a newline
echo ‘This will not expand: \n a newline’;

// Outputs: Variables do not $expand $either
echo ‘Variables do not $expand $either’;
?>

5.1.3 Double-Quoted Strings
Double-quoted strings interpolate variables and expand the many PHP escape sequences. Table
5.1 lists the escape sequences recognized by PHP in double-quoted strings.

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