$re = '/<TEXT>\s*begin \d+ (?>[^e]+|e(?!nd\s*<\/TEXT>))*end\s*<\/TEXT>/m';
$str = '<HTML>
<BODY STYLE="font: 10pt Times New Roman, Times, Serif">
<TEXT>
begin 644 h52992h5299202.gif
M1TE&.#EA>P`>`,0``\']_?S\\_/^_O[P\\/#[^_OU]?7Q\\?\'X^/CY^?GZ^OK\\_/
MSV]O;T]/3]_?WR\\O+U!04````/___P``````````````````````````````
M`````````````````````````"\'Y!```````+`````![`!X```7_8"2.9&F>
M:*JN+"DP22O/=&W?Z`(M>.__0-4`T@@:C\\A689=L-0B$!`(!`""@S:P)$M"B
M!(#"$$(NEP,`0E,AR!X@"N_I`1D$&-6JM,H8PXX-$`5-`@9=<B8(#\'$K5$,\'
M1H$0:D@,$#&(*PD`*0(.<$8!@D@*$`:9*P)D*@D0G$&?"$A+KZ@H;PPJ;[4^
MI09M1Z)%MBB6E"<(ID8&9,!!`G;$7T-?2P[./F]DLD8`$)`F"@0\'",->;X<E
M")\\,V#W0`T.\\/IX#YA$"8F2BEW)+/",:(!#EX!@0\'0!:S>OQ!F"$!&+L%(C#
MS($<4<#`5#S@SD:#`@#:&#A%P%6W22):_QG@J(`/&7`N`#@`U[+`J0A4`-P[
M`0V"B`,&!A2`^>.%F5\\*@S08*4+!$`,`%HS9$4/``2MAIA:P=(;?O@0=?T*P
M&&%;DP1>XT%H]P/MO@!3S;P-P$RNF0$+$+3:!X!!7:@=EV`BXQ!)L@()I)*Q
MPTT&@@(!O)K"<X``5[D.%E2YDN!O90+F7I(8N)C1"&%BQQ:X$@P"L%:11[5`
M4%=NX8!0")@N`8:MB0*W11#X-("7@W3XELBU$SER8QFETI5<F$(!,Z$<(WB[
M*2W"1Z(F31#(`[DYLT$T1)F>?AIYB5)<G*D:8+`["?8T"(3M%&U$4A%1I:#-
M??%09Y]V*/5`VU0*WF`B@@X.KN"4(%!X0]^!*\'A37PT*$\'6")?(-L9,*$Y8Q
MP&X8DJ##B$DL04(IZ,U``&0&%+!?BH9D$D4)V:68A"KN^2BD#R4%-^21-O2(
\'Y)(TA```.S\\_
`
end
</TEXT>
<TEXT>losses occurring in the third quarter and from weather </TEXT>
</BODY>';
$subst = "<TEXT><\/TEXT>";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php