A string of characters—a string—is probably the most commonly used data type when developing scripts, and PHP provides a large library of string functions to help transform, manipulate, and otherwise manage strings. We introduced PHP strings earlier, in Section 2.1.1. Here, we examine string literals in more detail and describe some of the useful string functions PHP provides.

String Literals

As already shown in previous examples, enclosing characters in single quotes or double quotes can create a string literal. Single-quoted strings are the simplest form of string literal; double-quoted strings are parsed to substitute variable names with the variable values and allow characters to be encoded using escape sequences. Single-quoted strings don’t support all the escape sequences, only \' to include a single quote and \\ to include a backslash.

Tab, newline, and carriage-return characters can be included in a double-quoted string using the escape sequences \t, \n, and \r, respectively. To include a backslash, a dollar sign, or a double quote in a double-quoted string, use the escape sequences \\, \$, or \".

Other control characters and characters with the most significant bit set can be included using escaped octal or hexadecimal sequences. For example, to include the umlauted character ö, the octal sequence \366 or the hexadecimal sequence \xf6 are used:

//Print a string that includes a lowercase //o with the umlaut mark echo "See you at the G\xf6teborg Film Festival"; ...

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