in the current (CVS) version of PHP4, this function
is definend in php4/ext/mysql/php_mysql.c
and implemented in php4/ext/mysql/php_mysql.c

it is documented in mysql.xml

a german translation is available

a japanese translation is available

there is a proto in latest PHP3 source:

int mysql_pconnect([string hostname[:port][:/path/to/socket]] [, string username] [, string password]) Open a persistent connection to a MySQL Server

there is a proto in latest PHP4 source:

int mysql_pconnect([string hostname[:port][:/path/to/socket]] [, string username] [, string password]) Open a persistent connection to a MySQL Server