> ## Documentation Index > Fetch the complete documentation index at: https://docs.syntblaze.com/llms.txt > Use this file to discover all available pages before exploring further. # PHP string A string in PHP is implemented as an array of bytes coupled with an integer indicating the length of the buffer. Because PHP does not dictate a specific character encoding at the core language level, a "character" in a standard PHP string is strictly equivalent to a single byte. Consequently, native string functions operate on byte values rather than Unicode code points. PHP provides four syntactical methods for defining string literals: **1. Single Quoted** Single quotes create literal strings. Escape sequences (other than `\'` and `\\`) and variables are not evaluated or parsed. ```php theme={"dark"} $literal = 'This is a literal string.\n Variables like $foo are ignored.'; ``` **2. Double Quoted** Double quotes instruct the PHP engine to parse the string for escape sequences (e.g., `\n`, `\t`, `\x0F`) and interpolate variables. ```php theme={"dark"} $foo = 'bar'; $parsed = "This string evaluates escape sequences\n and variables: $foo"; ``` **3. Heredoc** Heredoc syntax behaves identically to double-quoted strings but is designed for multiline declarations without requiring escaping for internal quotes. It is initialized using `<<<` followed by an identifier. ```php theme={"dark"} $foo = 'bar'; $heredoc = << 'data']; $object = new stdClass(); $object->property = 'value'; // Simple syntax $simple = "I ate an $noun."; // Complex syntax (required to separate the variable from the literal 's') $complex = "I ate two {$noun}s."; // Complex syntax for arrays and objects $dynamic = "Value: {$array['key']} and {$object->property}"; ``` ## String Concatenation PHP utilizes the dot (`.`) operator for string concatenation. The concatenating assignment operator (`.=`) appends the right-hand argument to the existing left-hand string variable, mutating it in place. ```php theme={"dark"} $prefix = "Byte"; $suffix = "Buffer"; // Concatenation operator $combined = $prefix . $suffix; // "ByteBuffer" // Concatenating assignment operator $combined .= " Length"; // "ByteBuffer Length" ``` ## Byte Access and Mutation Because PHP strings are zero-indexed byte arrays, individual bytes can be accessed and mutated using array offset syntax (`[]`). ```php theme={"dark"} $string = "PHP"; $firstByte = $string[0]; // 'P' // Mutating a specific byte $string[2] = 'X'; // $string is now "PHX" ``` *Note: Modifying a string via byte offsets does not account for multibyte character encodings (like UTF-8). Mutating a byte within a multibyte character will result in a corrupted character payload.* ## Memory and Length Mechanics The length of a string is determined by its byte count, not its character count. The native `strlen()` function returns the size of the internal byte array. ```php theme={"dark"} $ascii = "Hello"; echo strlen($ascii); // Outputs: 5 $utf8 = "Héllö"; echo strlen($utf8); // Outputs: 7 (due to multibyte characters) ``` To accurately measure or manipulate strings containing multibyte characters, developers must utilize the `mbstring` extension (e.g., `mb_strlen()`, `mb_substr()`), which parses the byte array according to a specified character encoding. On 64-bit builds of PHP, the maximum length of a string is bounded only by the system's available memory and the `memory_limit` directive in `php.ini`. On 32-bit builds, the maximum string length is strictly 2GB (2,147,483,647 bytes).
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