- is_numeric: documentation ( source)
<?php
print "is_numeric(NAN) ? " . (is_numeric(NAN) ? "true\n" : "false\n");
print "NAN == 0 ? " . (NAN == 0 ? "true\n" : "false\n");
print "NAN == 1 ? " . (NAN == 1 ? "true\n" : "false\n");
print "NAN === 0 ? " . (NAN === 0 ? "true\n" : "false\n");
print "NAN === 1 ? " . (NAN === 1 ? "true\n" : "false\n");
print "NAN == NAN ? " . (NAN == NAN ? "true\n" : "false\n");
print "NAN === NAN ? " . (NAN === NAN ? "true\n" : "false\n");
print "(int) NAN = " . ((int) NAN) . "\n";