Strings

Single quoted

The easiest way to specify a simple string is to enclose it in single quotes (the character ').

To specify a literal single quote, you will need to escape it with a backslash (\), like in many other languages. If a backslash needs to occur before a single quote or at the end of the string, you need to double it. Note that if you try to escape any other character, the backslash too will be printed! So usually there is no need to escape the backslash itself.

echo 'this is a simple string';
echo 'You can also have embedded newlines in strings,
like this way.';
echo 'Arnold once said: "I\'ll be back"';
// output: ... "I'll be back"
echo 'Are you sure you want to delete C:\\*.*?';
// output: ... delete C:\*.*?
echo 'Are you sure you want to delete C:\*.*?';
// output: ... delete C:\*.*?
echo 'I am trying to include at this point: \n a newline';
// output: ... this point: \n a newline

Double quoted

If the string is enclosed in double-quotes ("), PHP understands more escape sequences for special characters:

Again, if you try to escape any other character, the backslash will be printed too!

But the most important pre of double-quoted strings is the fact that variable names will be expanded. See string parsing for details.

Heredoc

Another way to delimit strings is by using heredoc syntax ("<<<"). One should provide an identifier after <<<, then the string, and then the same identifier to close the quotation.

The closing identifier must begin in the first column of the line. Also, the identifier used must follow the same naming rules as any other label in PHP: it must contain only alphanumeric characters and underscores, and must start with a non-digit character or underscore.

Heredoc text behaves just like a double-quoted string, without the double-quotes. This means that you do not need to escape quotes in your here docs, but you can still use the escape codes listed above. Variables are expanded, but the same care must be taken when expressing complex variables inside a here doc as with strings.

Příklad 7-2. Heredoc string quoting example <?php $str = <<<EOD Example of string spanning multiple lines using heredoc syntax. EOD; /* More complex example, with variables. */ class foo { var $foo; var $bar; function foo() { $this->foo = 'Foo'; $this->bar = array('Bar1', 'Bar2', 'Bar3'); } } $foo = new foo(); $name = 'MyName'; echo <<<EOT My name is "$name". I am printing some $foo->foo. Now, I am printing some {$foo->bar[1]}. This should print a capital 'A': \x41 EOT; ?>

Variable parsing

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

There are two types of syntax, a simple one and a complex one. The simple syntax is the most common and convenient, it provides a way to parse a variable, an array value, or an object property.

The complex syntax was introduced in PHP 4, and can be recognised by the curly braces surrounding the expression.

$beer = 'Heineken';
echo "$beer's taste is great"; // works, "'" is an invalid character for varnames
echo "He drank some $beers"; // won't work, 's' is a valid character for varnames
echo "He drank some ${beer}s"; // works

$fruits = array( 'strawberry' => 'red' , 'banana' => 'yellow' );

// note that this works differently outside string-quotes.
echo "A banana is $fruits[banana].";

echo "This square is $square->width meters broad.";

// Won't work. For a solution, see the complex syntax.
echo "This square is $square->width00 centimeters broad.";

$great = 'fantastic';
echo "This is { $great}"; // won't work, outputs: This is { fantastic}
echo "This is {$great}";  // works, outputs: This is fantastic
echo "This square is {$square->width}00 centimeters broad."; 
echo "This works: {$arr[4][3]}";     

// This is wrong for the same reason
// as $foo[bar] is wrong outside a string. 
echo "This is wrong: {$arr[foo][3]}"; 

echo "You should do it this way: {$arr['foo'][3]}";
echo "You can even write {$obj->values[3]->name}";
echo "This is the value of the var named $name: {${$name}}";

String access by character

Characters within strings may be accessed by specifying the zero-based offset of the desired character after the string in curly braces.

Příklad 7-3. Some string examples <?php /* Assigning a string. */ $str = "This is a string"; /* Appending to it. */ $str = $str . " with some more text"; /* Another way to append, includes an escaped newline. */ $str .= " and a newline at the end.\n"; /* This string will end up being '<p>Number: 9</p>' */ $num = 9; $str = "<p>Number: $num</p>"; /* This one will be '<p>Number: $num</p>' */ $num = 9; $str = '<p>Number: $num</p>'; /* Get the first character of a string */ $str = 'This is a test.'; $first = $str{0}; /* Get the last character of a string. */ $str = 'This is still a test.'; $last = $str{strlen($str)-1}; ?>