Строки

Синтаксис

Строка может быть определена тремя различными способами.

• одинарными кавчками

• двойными кавычками

• heredoc-синтаксисом

echo ''это простая строка';
echo 'Вы можете вставлять в строки символ новой строки
таким образом';
echo 'Однажды Арнольд сказал: "I\'ll be back"';
// вывод: ... "I'll be back"
echo 'Вы уверены, что хотите удалить C:\\*.*?';
// вывод: ... удалить C:\*.*?
echo 'Вы уверены, что хотите удалить C:\*.*?';
// вывод: ... удалить C:\*.*?
echo 'Я пытаюсь вставить в этой точке: \n символ новой строки';
// вывод: ... в этой точке: \n символ новой строки

$beer = 'Heineken';
echo "$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}}";

Useful functions and operators

Strings may be concatenated using the '.' (dot) operator. Note that the '+' (addition) operator will not work for this. Please see String operators for more information.

There are a lot of useful functions for string modification.

See the string functions section for general functions, the regular expression functions for advanced find&replacing (in two tastes: Perl and POSIX extended).

There are also functions for URL-strings, and functions to encrypt/decrypt strings (mcrypt and mhash).

Finally, if you still didn't find what you're looking for, see also the character type functions.

Converting to string

You can convert a value to a string using the (string) cast, or the strval() function. String conversion is automatically done in the scope of an expression for you where a string is needed. This happens when you use the echo() or print() functions, or when you compare a variable value to a string.

A boolean TRUE value is converted to the string "1", the FALSE value is represented as "" (empty string). This way you can convert back and forth between boolean and string values.

An integer or a floating point number is converted to a string representing the number with its digits (includig the exponent part for floating point numbers).

Arrays are always converted to the string "Array", so you cannot dump out the contents of an array with echo() or print() to see what is inside them. See the information below for more tips.

Objects are always converted to the string "Object". If you would like to print out the member variable values of an object for debugging reasons, read the paragraphs below. If you would like to find out the class name of which an object is an instance of, use get_class().

Resources are always converted to strings with the structure "Resource id #1" where 1 is the unique number of the resource assigned by PHP during runtime. If you would like to get the type of the resource, use get_resource_type().

NULL is always converted to an empty string.

As you can see above, printing out the arrays, objects or resources does not provide you any useful information about the values themselfs. Look at the functions print_r() and var_dump() for better ways to print out values for debugging.

You can also convert PHP values to strings to store them permanently. This method is called serialization, and can be done with the function serialize(). You can also serialize PHP values to XML structures, if you have WDDX support in your PHP setup.

String conversion to numbers

When a string is evaluated as a numeric value, the resulting value and type are determined as follows.

The string will evaluate as a float if it contains any of the characters '.', 'e', or 'E'. Otherwise, it will evaluate as an integer.

The value is given by the initial portion of the string. If the string starts with valid numeric data, this will be the value used. Otherwise, the value will be 0 (zero). Valid numeric data is an optional sign, followed by one or more digits (optionally containing a decimal point), followed by an optional exponent. The exponent is an 'e' or 'E' followed by one or more digits.

$foo = 1 + "10.5";              // $foo is float (11.5)
$foo = 1 + "-1.3e3";            // $foo is float (-1299)
$foo = 1 + "bob-1.3e3";         // $foo is integer (1)
$foo = 1 + "bob3";              // $foo is integer (1)
$foo = 1 + "10 Small Pigs";     // $foo is integer (11)
$foo = 4 + "10.2 Little Piggies"; // $foo is float (14.2)
$foo = "10.0 pigs " + 1;        // $foo is float (11)
$foo = "10.0 pigs " + 1.0;      // $foo is float (11)

For more information on this conversion, see the Unix manual page for strtod(3).

If you would like to test any of the examples in this section, you can cut and paste the examples and insert the following line to see for yourself what's going on:

echo "\$foo==$foo; type is " . gettype ($foo) . "<br />\n";

Do not expect to get the code of one character by converting it to integer (as you would do in C for example). Use the functions ord() and chr() to convert between charcodes and characters.