Enable tracing a PostgreSQL connection

# pg_trace

(PHP 4 >= 4.0.1, PHP 5, PHP 7, PHP 8)

pg_trace — Enable tracing a PostgreSQL connection

### Description

pg_trace(
string `$filename`,
string `$mode` = "w",
?PgSql\Connection `$connection` = `null`,
int `$trace_mode` = 0
): bool

pg_trace() enables tracing of the PostgreSQL frontend/backend communication to a file. To fully understand the results, one needs to be familiar with the internals of PostgreSQL communication protocol.

For those who are not, it can still be useful for tracing errors in queries sent to the server, you could do for example grep '^To backend' trace.log and see what queries actually were sent to the PostgreSQL server. For more information, refer to the » PostgreSQL Documentation.

### Parameters

`filename`

  The full path and file name of the file in which to write the trace log. Same as in fopen().

`mode`

  An optional file access mode, same as for fopen().

`connection`

  An PgSql\Connection instance. When `connection` is `null`, the default connection is used. The default connection is the last connection made by pg_connect() or pg_pconnect().

  Warning

  As of PHP 8.1.0, using the default connection is deprecated.

`trace_mode`

  An optional trace mode with the following constants `PGSQL_TRACE_SUPPRESS_TIMESTAMPS` and `PGSQL_TRACE_REGRESS_MODE`

### Return Values

Returns `true` on success or `false` on failure.

### Changelog

Version | Description
--- | ---
8.3.0 | `trace_mode` has been added.
8.1.0 | The `connection` parameter expects an PgSql\Connection instance now; previously, a resource was expected.
8.0.0 | `connection` is now nullable.

### Examples

Example #1 pg_trace() example

`<?php
$pgsql_conn = pg_connect("dbname=mark host=localhost");
if ($pgsql_conn) {
pg_trace('/tmp/trace.log', 'w', $pgsql_conn);
pg_query("SELECT 1");
pg_untrace($pgsql_conn);
// Now /tmp/trace.log will contain backend communication
} else {
print pg_last_error($pgsql_conn);
exit;
}
?>`

### See Also

- fopen() - Opens file or URL
- pg_untrace() - Disable tracing of a PostgreSQL connection

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