Please add the full error message here.

My source no longer generates this error. Please read the full bug description. OBVIOUSLY the error was something to effect of:
`T' undeclared (first use in this function)
(Each undeclared identifier is reported only once
for each function it appears in.)

The line number in the source code was 1117

I need the full *original* error, so remove your hack and recompile again. It works fine here.

I have no more time to assist with this. Here is the information you requested. You fix this problem (which probably only occurs with certain versions of the imap headers, maybe only on Solaris) by adding the code I included, which will do nothing if T is already defined.
Or not...
It's up the powers that be that maintain this package.
Whatever.

Here's the error text:

/bin/sh /usr/share/src/php-4.3.2/libtool --silent --preserve-dup-deps --mode=compile /usr/share/src/php-4.3.2/meta_ccld  -Iext/imap/ -I/usr/share/src/php-4.3.2/ext/imap/ -DPHP_ATOM_INC -I/usr/share/src/php-4.3.2/include -I/usr/share/src/php-4.3.2/main -I/usr/share/src/php-4.3.2 -I/opt/netscape/plugins/include -I/usr/share/src/php-4.3.2/Zend -I/opt/sfw/include -I/opt/app/oracle/product/8.1.6/rdbms/public -I/opt/app/oracle/product/8.1.6/rdbms/demo -I/opt/app/oracle/product/8.1.6/network/public -I/usr/share/src/php-4.3.2/ext/xml/expat  -D_POSIX_PTHREAD_SEMANTICS -D_POSIX_PTHREAD_SEMANTICS -D_REENTRANT -I/usr/share/src/php-4.3.2/TSRM -DTHREAD=1  -O2 -I/opt/app/oracle/product/8.1.6/rdbms/demo -I/opt/app/oracle/product/8.1.6/rdbms/public -I/opt/app/oracle/product/8.1.6/network/public -pthreads -DZTS  -prefer-pic -c /usr/share/src/php-4.3.2/ext/imap/php_imap.c -o ext/imap/php_imap.lo
/usr/share/src/php-4.3.2/ext/imap/php_imap.c: In function `zif_imap_mail_copy':
/usr/share/src/php-4.3.2/ext/imap/php_imap.c:1117: `T' undeclared (first use in this function)
/usr/share/src/php-4.3.2/ext/imap/php_imap.c:1117: (Each undeclared identifier is reported only once
/usr/share/src/php-4.3.2/ext/imap/php_imap.c:1117: for each function it appears in.)
/usr/share/src/php-4.3.2/ext/imap/php_imap.c: In function `zif_imap_mail_move':
/usr/share/src/php-4.3.2/ext/imap/php_imap.c:1145: `T' undeclared (first use in this function)
/usr/share/src/php-4.3.2/ext/imap/php_imap.c: In function `zif_imap_createmailbox':
/usr/share/src/php-4.3.2/ext/imap/php_imap.c:1168: `T' undeclared (first use in this function)
/usr/share/src/php-4.3.2/ext/imap/php_imap.c: In function `zif_imap_renamemailbox':
/usr/share/src/php-4.3.2/ext/imap/php_imap.c:1192: `T' undeclared (first use in this function)
/usr/share/src/php-4.3.2/ext/imap/php_imap.c: In function `zif_imap_deletemailbox':
/usr/share/src/php-4.3.2/ext/imap/php_imap.c:1215: `T' undeclared (first use in this function)
/usr/share/src/php-4.3.2/ext/imap/php_imap.c: In function `zif_imap_subscribe':
/usr/share/src/php-4.3.2/ext/imap/php_imap.c:1648: `T' undeclared (first use in this function)
/usr/share/src/php-4.3.2/ext/imap/php_imap.c: In function `zif_imap_unsubscribe':
/usr/share/src/php-4.3.2/ext/imap/php_imap.c:1671: `T' undeclared (first use in this function)
*** Error code 1
make: Fatal error: Command failed for target `ext/imap/php_imap.lo'

If that constant is not defined, it's really something
broken in your c-client headers, not by any chance in PHP.

It is defined, in a file php did not include.

Top lines from /usr/include/mail.h

/*
 * Program:     Mailbox Access routines
 *
 * Author:      Mark Crispin
 *              Networks and Distributed Computing
 *              Computing & Communications
 *              University of Washington
 *              Administration Building, AG-44
 *              Seattle, WA  98195
 *              Internet: MRC@CAC.Washington.EDU
 *
 * Date:        22 November 1989
 * Last Edited: 13 November 2001
 *
 * The IMAP toolkit provided in this Distribution is
 * Copyright 2001 University of Washington.
 * The full text of our legal notices is contained in the file called
 * CPYRIGHT, included with this Distribution.
 */
#ifndef INCMAILH
#define INCMAILH 1

/* Build parameters */

#define CACHEINCREMENT 250      /* cache growth increments */
#define MAILTMPLEN 1024         /* size of a temporary buffer */
#define MAXMESSAGESIZE 65000    /* MS-DOS: maximum text buffer size
                                 * other:  initial text buffer size */
#define MAXUSERFLAG 64          /* maximum length of a user flag */
#define MAXAUTHENTICATORS 8     /* maximum number of SASL authenticators */


/* These can't be changed without changing code */

#define NUSERFLAGS 30           /* maximum number of user flags */
#define BASEYEAR 1970           /* the year time began on Unix DON'T CHANGE */
                                /* default for unqualified addresses */
#define BADHOST ".MISSING-HOST-NAME."
                                /* default for syntax errors in addresses */
#define ERRHOST ".SYNTAX-ERROR."


/* Coddle certain compilers' 6-character symbol limitation */

#ifdef __COMPILER_KCC__
#include "shortsym.h"
#endif


/* Function status code */

#define NIL 0                   /* convenient name */
#define T 1                     /* opposite of NIL */
#define LONGT (long) 1          /* long T */
#define VOIDT (void *) ""       /* void T */

/* Global and Driver Parameters */

Wild guess: You have mixed versions of c-client libs in your system, one is used during configure and one actually during make, and this we can't prevent. 

Clear up your system of any remrants of old c-client libs and headers and install the new version after you have read the instructions here:

http://www.php.net/imap

And pay lot of attention to the part about copying the libs/headers under their own directory, e.g. /usr/local/c-client/lib and /usr/local/c-client/include
and use --with-imap=/usr/local/c-client/ and it will work just fine.