FILTER_VALIDATE_EMAIL no es magia negra. Tiene un código detrás.
- void php_filter_validate_email(PHP_INPUT_FILTER_PARAM_DECL) /* {{{ */ 
- { 
- 	/* 
- 	 * The regex below is based on a regex by Michael Rushton. 
- 	 * However, it is not identical.  I changed it to only consider routeable 
- 	 * addresses as valid.  Michael's regex considers a@b a valid address 
- 	 * which conflicts with section 2.3.5 of RFC 5321 which states that: 
- 	 * 
- 	 *   Only resolvable, fully-qualified domain names (FQDNs) are permitted 
- 	 *   when domain names are used in SMTP.  In other words, names that can 
- 	 *   be resolved to MX RRs or address (i.e., A or AAAA) RRs (as discussed 
- 	 *   in Section 5) are permitted, as are CNAME RRs whose targets can be 
- 	 *   resolved, in turn, to MX or address RRs.  Local nicknames or 
- 	 *   unqualified names MUST NOT be used. 
- 	 * 
- 	 * This regex does not handle comments and folding whitespace.  While 
- 	 * this is technically valid in an email address, these parts aren't 
- 	 * actually part of the address itself. 
- 	 * 
- 	 * Michael's regex carries this copyright: 
- 	 * 
- 	 * Copyright © Michael Rushton 2009-10 
- 	 * http://squiloople.com/ 
- 	 * Feel free to use and redistribute this code. But please keep this copyright notice. 
- 	 * 
- 	 */ 
- 	pcre2_code *re = NULL; 
- 	pcre2_match_data *match_data = NULL; 
- 	uint32_t capture_count; 
- 	zend_string *sregexp; 
- 	int rc; 
- 	const char regexp0[] = "/^(?!(?:(?:\\x22?\\x5C[\\x00-\\x7E]\\x22?)|(?:\\x22?[^\\x5C\\x22]\\x22?)){255,})(?!(?:(?:\\x22?\\x5C[\\x00-\\x7E]\\x22?)|(?:\\x22?[^\\x5C\\x22]\\x22?)){65,}@)(?:(?:[\\x21\\x23-\\x27\\x2A\\x2B\\x2D\\x2F-\\x39\\x3D\\x3F\\x5E-\\x7E\\pL\\pN]+)|(?:\\x22(?:[\\x01-\\x08\\x0B\\x0C\\x0E-\\x1F\\x21\\x23-\\x5B\\x5D-\\x7F\\pL\\pN]|(?:\\x5C[\\x00-\\x7F]))*\\x22))(?:\\.(?:(?:[\\x21\\x23-\\x27\\x2A\\x2B\\x2D\\x2F-\\x39\\x3D\\x3F\\x5E-\\x7E\\pL\\pN]+)|(?:\\x22(?:[\\x01-\\x08\\x0B\\x0C\\x0E-\\x1F\\x21\\x23-\\x5B\\x5D-\\x7F\\pL\\pN]|(?:\\x5C[\\x00-\\x7F]))*\\x22)))*@(?:(?:(?!.*[^.]{64,})(?:(?:(?:xn--)?[a-z0-9]+(?:-+[a-z0-9]+)*\\.){1,126}){1,}(?:(?:[a-z][a-z0-9]*)|(?:(?:xn--)[a-z0-9]+))(?:-+[a-z0-9]+)*)|(?:\\[(?:(?:IPv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){7})|(?:(?!(?:.*[a-f0-9][:\\]]){7,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?)))|(?:(?:IPv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){5}:)|(?:(?!(?:.*[a-f0-9]:){5,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3}:)?)))?(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))(?:\\.(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))){3}))\\]))$/iDu"; 
- 	const char regexp1[] = "/^(?!(?:(?:\\x22?\\x5C[\\x00-\\x7E]\\x22?)|(?:\\x22?[^\\x5C\\x22]\\x22?)){255,})(?!(?:(?:\\x22?\\x5C[\\x00-\\x7E]\\x22?)|(?:\\x22?[^\\x5C\\x22]\\x22?)){65,}@)(?:(?:[\\x21\\x23-\\x27\\x2A\\x2B\\x2D\\x2F-\\x39\\x3D\\x3F\\x5E-\\x7E]+)|(?:\\x22(?:[\\x01-\\x08\\x0B\\x0C\\x0E-\\x1F\\x21\\x23-\\x5B\\x5D-\\x7F]|(?:\\x5C[\\x00-\\x7F]))*\\x22))(?:\\.(?:(?:[\\x21\\x23-\\x27\\x2A\\x2B\\x2D\\x2F-\\x39\\x3D\\x3F\\x5E-\\x7E]+)|(?:\\x22(?:[\\x01-\\x08\\x0B\\x0C\\x0E-\\x1F\\x21\\x23-\\x5B\\x5D-\\x7F]|(?:\\x5C[\\x00-\\x7F]))*\\x22)))*@(?:(?:(?!.*[^.]{64,})(?:(?:(?:xn--)?[a-z0-9]+(?:-+[a-z0-9]+)*\\.){1,126}){1,}(?:(?:[a-z][a-z0-9]*)|(?:(?:xn--)[a-z0-9]+))(?:-+[a-z0-9]+)*)|(?:\\[(?:(?:IPv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){7})|(?:(?!(?:.*[a-f0-9][:\\]]){7,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?)))|(?:(?:IPv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){5}:)|(?:(?!(?:.*[a-f0-9]:){5,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3}:)?)))?(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))(?:\\.(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))){3}))\\]))$/iD"; 
- 	const char *regexp; 
- 	size_t regexp_len; 
-   
- 	if (flags & FILTER_FLAG_EMAIL_UNICODE) { 
- 		regexp = regexp0; 
- 		regexp_len  = sizeof(- regexp0 ) - 1;
- 	} else { 
- 		regexp = regexp1; 
- 		regexp_len  = sizeof(- regexp1 ) - 1;
- 	} 
-   
- 	/* The maximum length of an e-mail address is 320 octets, per RFC 2821. */ 
- 	if (Z_STRLEN_P(value) > 320) { 
- 		RETURN_VALIDATION_FAILED 
- 	} 
-   
- 	sregexp = zend_string_init(regexp, regexp_len, 0); 
- 	re = pcre_get_compiled_regex(sregexp, &capture_count); 
- 	zend_string_release_ex(sregexp, 0); 
- 	if (!re) { 
- 		RETURN_VALIDATION_FAILED 
- 	} 
- 	match_data = php_pcre_create_match_data(capture_count, re); 
- 	if (!match_data) { 
- 		RETURN_VALIDATION_FAILED 
- 	} 
- 	rc = pcre2_match(re, (PCRE2_SPTR)Z_STRVAL_P(value), Z_STRLEN_P(value), 0, 0, match_data, php_pcre_mctx()); 
- 	php_pcre_free_match_data(match_data); 
-   
- 	/* 0 means that the vector is too small to hold all the captured substring offsets */ 
- 	if (rc < 0) { 
- 		RETURN_VALIDATION_FAILED 
- 	} 
-   
- } 
- /* }}} */ 
Pórtalo a javascript. Si quieres que te quede más limpio el código para trabajar crea una carpetas libs y añades el código con Etiqueta script src ="libs/filtros/f_email.js">finEtiquetaScript