关于sprintf函数，官网说失败的时候会返回false。一直没遇到了，原来占位符比参数多就会返回false。

php -r 'var_dump(sprintf("%s|%s", 11, 22));'
string(5) "11|22"
MacBook-Pro-6:~ chuanbo7$ php -r 'var_dump(sprintf("%s|%s", 11));'
PHP Warning:  sprintf(): Too few arguments in Command line code on line 1

Warning: sprintf(): Too few arguments in Command line code on line 1
bool(false)
MacBook-Pro-6:~ chuanbo7$ php -r 'var_dump(sprintf("%s|%s", 11, 22, 33));'
string(5) "11|22"