(PHP 7, PHP 8)
IntlChar::isIDStart — Check if code point is permissible as the first character in an identifier
$codepoint): ?boolDetermines if the specified character is permissible as the first character in an identifier according to Unicode (The Unicode Standard, Version 3.0, chapter 5.16 Identifiers).
true for characters with general categories "L" (letters) and "Nl" (letter numbers).
codepointThe int codepoint value (e.g. 0x2603 for U+2603 SNOWMAN), or the character encoded as a UTF-8 string (e.g. "\u{2603}")
Returns true if
codepoint may start an identifier, false if not. Returns null on failure.
示例 #1 Testing different code points
<?php
var_dump(IntlChar::isIDStart("A"));
var_dump(IntlChar::isIDStart("$"));
var_dump(IntlChar::isIDStart("\n"));
var_dump(IntlChar::isIDStart("\u{2603}"));
?>以上示例会输出：
bool(true) bool(false) bool(false) bool(false)
IntlChar::PROPERTY_ID_START